apt / apt-get

Debian Package Manager

• sudo apt update
• sudo apt --upgradable (will show which packages will be updated)

.bash_profile

This is your login script

• Can edit .bash_profile to make Aliases permanent for your user.

.bashrc

Used to customize the shell - loaded whenever you open a new instance of the shell

• alias ls=’echo;ls –alF; echo; echo "Listed on: "$(date);echo’

• alias dir=’clear;ls’
  • alias dir=’ls –lF | grep ^d’

• In Terminal to temporarily prevent an Alias from running, precede the aliased command with a backslash, ex: "\ls"

• Edit .bashrc or .bash_profile to make Aliases permanent for your user
  • Note: If your alias is not working, move your User Specific Aliases and Functions BELOW where the globals are loaded in your .bashrc.

• If you’ve modified .bashrc and wish to "reload" it, use this command:
  • ". .bashrc"

• Add this line to change the Root User Prompt Color to Red:
  • PS1="[\033[01;31m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]]# "

You can also just use /etc/profile instead of .bashrc or .bash_profile to edit your bash prompt, add aliases, etc. On a Raspberry Pi the custom Root Prompt is placed in /etc/bash.bashrc while the User prompt is placed in ~/.bashrc

In RHEL 7 for example the Alias 'll' with defaults of '-l --color=auto', lives in: /etc/profile.d/colorls.sh.

.htaccess

Example of .htaccess file:

Another Example of .htaccess file:

Another Example of .htaccess file, deny IP or range:

Note: Now create .htpasswd, see .htpasswd below

Note: changes to .htaccess are immediate, no httpd restart necessary

Note: you can also use: require user for specific users

Troubleshooting:

• Most common mistake: incorrect path to .htpasswd file, double-check path is correct
• Another common mistake: misspelling the .htaccess file (ex. .htacess)
• Apache config file: /etc/httpd/conf/httpd.conf – scroll down and make sure "AllowOverride" is NOT set to "None" but rather "All" – restart httpd

.htpasswd

Create the file:

• htpasswd –c .htpasswd <username>

To add users afterwards:

• htpasswd .htpasswd <username2>

.profile

Create to automatically load .bashrc in the shell:

• ". .bashrc"

~/.bash_profile should be super-simple and just load .profile and .bashrc (in that order)

~/.profile has the stuff NOT specifically related to bash, such as environment variables (PATH and friends)

~/.bashrc has anything you'd want at an interactive command line. Command prompt, EDITOR variable, bash aliases for your use. It must NOT output anything

Anything that should be available to graphical applications OR to sh (or bash invoked as sh) MUST be in ~/.profile

Anything that should be available only to login shells should go in ~/.profile

ACL (adding Access Control List functionality)

Before using ACLs for a file or directory, the partition for the file or directory must be mounted with ACL support:

• mount –t ext3 –o acl <device-name> <partition>
• or /etc/fstab:LABEL=/work /work ext3 acl 1 2

The file system being exported by an NFS server supports ACLs by default

Set ACLs for files and directories:

• setfacl –m <rules> <files/directories>
• setfacl –m g:accounting:rwx /project/payments

Set a Default ACL for a directory:

• setfacl –m d:<rules> <files/directories>
• setfacl –m d:g:fac:rwx /homes

Remove an ACL for files and directories:

• setfacl –x <rules> <files/directories>
• setfacl –x g:accounting /project/payments

Remove all extended ACL entries:

• setfacl –b <file/directory>
• setfacl –-remove-all <file/directory>

Remove all the Default ACL entries:

• setfacl –k <file/directory>
• setfacl –-remove-default <file/directory>

Set ACLs Recursively:

• setfacl –R –m <file/directory>
• setfacl –R –m g:fac:rwx /homes

View ACLs for files and directories:

• getfacl <file/directory>
• getfacl /project/payments

Note: in an long directory listing you ACLs are indicated by a "+" at the end

Active Directory: Joining a Linux Machine to AD

Adding new Hard Drive / Local Storage

1. Add drive to server
2. Once booted, fdisk –l to see new drive
3. Create Partitions: fdisk
   1. fdisk /dev/<newdisk>
   2. n (add a new partition)
   3. v (verify)
   4. p (print partition table)
   5. w (write partition table to disk)
4. Make file system:
   1. mkfs.ext3 –v /dev/<newdisk>
   2. mkfs –v –t ext3 /dev/<newdisk>
5. Make local directory: mkdir mymount
6. Mount new drive:
   1. mount /dev/<newdisk> /mymount
7. Make mount permanent:
   1. edit /etc/fstab:
      1. /dev/ /mymount defaults 1,1

Add a User

Useradd (See User Administration below)

Alias

Create temp alias: alias newcommand=’yourcommand –arguments’

Remove temp alias: unalias newcommand

Aliases with switches: alias ‘rm –rf’="rm –rfv"

Disable an alias for the current session (ex. Preventing cp overwrite prompt): unalias cp / unalias <alias>

Temporarily Bypass an Alias:

• Precede term with a \
• Ex.: \rm

To Load your new aliases immediately from .bashrc: source ~/.bashrc or . .bashrc

Aliases, system-wide for all users, edit:

• /etc/bashrc
• Then Add this, if it’s not there already, to your .bashrc file:

Some Examples:

• alias l.='ls -d .' # Show ONLY hidden files.
• alias lx='ls -X' # ls, sort by extension.
• alias duh='du -h -max-depth=1' # Total size of this directory.
• alias ll='ls -hlrt --group-directories-first --color=auto' # Directories at top, size in human readable
• alias gh='history|grep' # Grep History for term, usage: gh vi

Finding Rogue Alias Declarations:

• If you checked for the offending alias in all the usual places: ~/.bashrc, ~/.bash_profile, /etc/bashrc and /etc/profile and it's not there, use this command to search /etc: grep -r '^alias <command>' /etc, ex: grep -r '^alias ll' /etc

In RHEL 7 for example the Alias 'll' with defaults of '-l --color=auto', lives in: /etc/profile.d/colorls.sh. So if your Alias is being overridden, check under /etc/profile.d/ first.

Apache / httpd

Restart Apache: apachectl restart

Alternate: service httpd restart

Apache Version: apachectl –v or apachectl –V (Verbose output including the compile settings)

Apache Version on other systems: try httpd –v or apache2 –v or apache2ctl –v

Test Apache / HTTP configuration file for errors: apachectl configtest

RHEL 7 / CentOS 7:

• Start Apache at Boot: systemctl enable httpd.service
• Disable Apache Start at Boot: systemctl disable httpd.service
• Start Apache: systemctl start httpd.service , options: < start | stop | restart >
• To verify that the httpd service is running: systemctl is-active httpd.service

Apache HTML files

/var/www/html or /usr/local/apache/htdocs (See User Administration below)

Authentication – setup

To setup LDAP or authentication types, in general, use:

• authconfig-gtk (GUI)
• authconfig (Text based)

bmon – Command Line

Powerful Network Bandwidth Monitoring and Debugging Tool for Linux: bmon

Command Line Switch (-p): bmon -p <network interface to display>

Command Line Switch (-b): bmon -b <Use Bits per Second (Mb, Kb) instead of Bytes per Second (Mib, Kib)>

Interface Command: d - for Detailed statistics

Interface Command: i - for additional Information

Interface Command: Shift+q - for Quick reference

Bookmark – Command Line, Terminal

To bookmark the current directory use: pushd .

To return to the bookmarked directory use: popd

Change a user password

passwd

Check your environment, path variables

env

Command line Calendar

To display the prev, cur, next month calendar: cal -3

To display the Year calendar: cal –y

Command line editors

pico, nano, vi, vim

Compare Files (diff)

cmp file1 file2

• No output if files are same
• If different, lists the byte number and line #

diff file1 file2

• No output if files are same
• If different, lists differing lines

diff --ignore-space-change file1 file2

• a.k.a. -b
• Ignores changes in amount of white space between files
• See here

diff --side-by-side –-suppress-common-lines file1 file2

• --side-by-side a.k.a. -y
• Offers a 2-column view of the files showing differences
• Can create: alias diffs=’diff –side-by-side –suppress-common-lines’

Console Resolution – changing

Changing Framebuffer or Text Console Display Line Resolution:

• If using grub, edit /boot/grub/menu.lst add vga=791 (or other value) after the end of the Kernel line
• If using lilo, edit lilo.conf and use vga=ext

Copy – Copy files and Directories

Recursive Copy All files in Current Dir to /tmp: cp –r * /tmp

CPU Information

Number of CPUs: nproc

Get CPU information: cat /proc/cpuinfo

CPU Information / Cores / Threads per Core / etc.: lscpu

Is this Server a Virtual Machine?: dmidecode | grep –i product

Get the number of CPUs: grep –i "physical id" /proc/cpuinfo | sort –u | wc -l

Is Hyperthreading enabled? Show Threads Per Core: lscpu | grep –i thread

XSOS tool for sysadmins (shows all this + more): wget people.redhat.com/rsawhill/rpms/latest-xsos.rpm

Crontab, List crontab files

User crontab files are kept in: /var/spool/cron

crontab –lu <username>

• –r to remove current crontab
• –e to edit current crontab
• –l to list the crontab file
• # to comment a line

Crontab Positions and what they mean (1 2 3 4 5 6-task):

Ex.: Delete all files in your tmp folder every morning at 4:45am, Mon-Fri: "45 4 * * 1-5 rm /home//tmp/*"

Ex.: to run a job every 5 minutes: "*/5 * * * * /my/command"

Note: It’s best to use the full path to any commands given, ex: /usr/bin/rm /home//tmp/*

Note: If you don’t want an e-mail sent every time a cron job runs use: "45 4 * * * rm /home//tmp/*>/dev/null 2>&1"

Note: To collect the cron execution in a log file: "45 4 * * * rm /home//tmp/*>/home//cronlogs/clean_tmp_dir.log"

Current Login Session Info

who –umH or w

Cut

Say you have a text file with lines of e-mail addresses and you only want the login names:

Run: cat File.txt | cut –d’@’ –f1

Where: d = delimiter, -f1 is the field number

Produces:

Date (Show Date and Time, Set Date and Time)

Show the Date and Time: date

Set the Date and Time: date –s "02/16/2006 16:11:00"

Delete / Remove a Directory and it’s contents

rm –r –v mydir/ = recursive, verbose

Delete a User

userdel (See User Administration below)

DHCPd

On Redhat 4 (Standard Install)

• Start: /usr/sbin/dhcpd or /etc/rc.d/init.d/dhcpd start
• Restart dhcpd: kill –SIGTERM <pid of dhcpd>
  • pid found in: /var/run/dhcpd.pid
  • Conf File: /etc/dhcpd.conf
  • Leases File: /var/lib/dhcp/dhcpd.leases

If you wish to test the configuration for any oddities, you can start dhcpd with the debugging mode. Typing the command below will allow you to see exactly what is going on with the server. Boot up a client. Take a look at the console of the dhcp server and you will see a number of debugging messages appear on the screen:

• /usr/sbin/dhcpd –d –f

Other Locations:

• dhcpd.conf = /etc/dhcpd/dhcpd.conf
• leases = /var/dhcpd/dhcpd.leases

Directory Listing All w/ Folder, Executable, Links, DIR

ls –alF

Show only Directories:

• ls –ld * / (Keeps color codings)
• ls –lF | grep ^d or ls –l | grep ^d
• find . –type d

Show only the Number of Directories: ls –lF | grep ^d | wc

Display File Size in Human Readable Format: ls –lh

Display File UID and GID instead of User and Group: ls –n

Display One File Per Line: ls –1

Disk space, file system disk space usage, file system type (ex. Ext3, etx4..)

Simple Summary of Disk Usage in the Current Folder: du –hs

Directory Summary of Specified Directory: du –hsc <mydir>, ex. du –hsc music

Directory Summary w/ Subdirectory Summary: du –hc <mydir w/ subdirs>, see abve

Directory Summary w/ Ind. File Summary: du –hac <mydir>

Display the Kernel Ring buffer (prints out Bootup messages)

dmesg

DNS (named)

DNS Server Control:

• service named start {start|stop|status|restart|condrestart|reload|probe}
• /etc/init.d/named start {see above}

Flush DNS Server Cache: rndc flush

Environment Variables

Export Environment Variables on System Reboot:

• Add something like this to /etc/profile:
  • export WSHOME=/var/tomcat/webapps/idm
  • export JAVA_HOME=/usr/java/jdk1.6.0_03
  • export BASEDIR=/var/tomcat
• After reboot they will be exported system-wide

For Regular Users, Edit one of these files:

• /home/user/.bash_profile (~/.bash_profile) – this personal initialization file is executed when you log into the system
• /home/user/.basrc (~/.bashrc) – this is the individual per-interactive-shell startup file
• Note: then logoff and logon again or just run: . .bash_profile to reload environment changes

ethtool

Display or change Ethernet card settings

Can easily get your Link Speed, Duplex, etc.

fdisk, Display Drive / Partition information

fdisk –l

Alternatively: dmesg | grep hd or dmesg | grep sd

File Descriptors

To increase file descriptors on Red Hat systems:

• echo 64000 > /proc/sys/fs/file-max
• ulimit –n 64000

To increase file descriptors in the Kernel on Red Hat systems:

• add fs.file-max = 65536 to /etc/sysctl.conf

After making changes, reboot or sysctl –p

Check your user limits: Sign in as user, issue: ulimit –n

File Perusal Filter (Less), opposite of More

ls | less (less allows scrolling by line or page)

In less, use ‘/’ to search for a pattern: /searchterm

Default file system

RHEL5: ext3

RHEL6: ext4

RHEL7: xfs

File Type Determination

file <filename>

Find

Find all files w/ index in the name & htm in the extension, no regard to case:

• find / -iname "*index*.htm*" –print

Find all files or directories modified in the last 24 hours:

• find . –mtime 0

Search the whole file system for all files being modified / accessed on Jan 26,2006:

• touch –amt 200601260000 /tmp/ref1
• touch –amt 200601262359 /tmp/ref2
• find / -type f –newer /tmp/ref1 –a ! –newer /tmp/ref2

Find all .txt files and show file datetime stamp sorted:

• find / -iname "*.txt" | xargs ls -ltr

Find file by filename

whereis <filename>

Firewall (iptables)

/etc/sysconfig/iptables = firewall rules file

To Enable logging to an Alternate File (ex. Iptables.log) the default = /var/log/messages:

• Edit: /etc/syslog.conf
• Add this line to the end: kern.warning /var/log/iptables.log
• Restart syslog: /etc/init.d/syslog restart

To Enable iptables logging:

• Edit: /etc/sysconfig/iptables
• Add this line before the REJECT or DROP Line(s) – Log and Drop in that order:
  • A RH-Firewall-1-INPUT –j LOG –log-prefix "** Denied Input **"
  • A RH-Firewall-1-INPUT –j REJECT –reject-with icmp-host-prohibited
  • Restart iptables: service iptables restart

To List iptable Rules with Line Numbers: iptables –L –line-numbers

RHEL / CentOS 7:

• systemctl status firewalld = Check the firewall status
• firewall-cmd --state = Checks if firewall-cmd can connect to the daemon
• systemctl disable firewalld = Disables the system firewall
• systemctl stop firewalld = Stop the firewall
• systemctl start firewalld = Start the firewall

Gawk – Pattern Matching

Return only the usernames (9th column) and Ips (11th column) for those people who were able to login to ssh by searching the secure.x files

• grep "Accepted password for" secure* | gawk ‘{print $9, $11}’

Graphical Login / startx - Kill the GUI

Enter a virtual terminal and then kill the GUI:

• Ctrl-Alt-F2
• init 3

init 5 = starts GUI again

Ctrl-Alt-F7 is where the GUI usually is

Grep

Find all occurrences of in file(s), case-insensitive:

• grep –i “<string>” files.*

Find all IP’s in 192.215. range:

• grep "192\.195\." *
• Note: "." Is special char for any char

Find (using Extended Regular Expressions) this OR that, ignore case:

• grep –iE ‘this|that’ *
• Note: Can use egrep instead of –E
  • egrep –v "this|that"
  • Find everything but (-v) this OR that. This works great at the end of a tail –f

Grep for a word and show the lines around the matching line:

• grep –B1 –A2 "keyword" <file>
• Where B1 = 1 Line Before and A2 = 2 Lines After the Matching Line

More Examples

Groups

List of groups is in: /etc/group

Fields:

• group_name : password : group_id : group_list1 , group_list2
• Ex: cdrom:x:24:student1,student2

List Groups a User belongs to:

• groups <username> , Ex. groups root

Show group ID of user: id –g jdoe

Show group ID to Group Name of user: id –gn jdoe

Show group ID and supplementary groups of a user: id –Gn root

Create a New Group: groupadd gDevelopers

• Add a New User to this Group: useradd –G gDevelopers hsimpson

• Add an Existing User to this Group: usermod –a –G gDevelopers bsimpson

Gzip / Gunzip / Compress / Expand Files

gunzip myfiles.gz

Ex. Write the uncompressed contents of README.gz to standard output. Pipe it into a pager for easy reading of a compressed file:

• gunzip -c README.gz | more

History

Search History for command: history | grep –i "<search term>"

Execute a command by its number: !<history number>

Prevent Saving your history upon shell Exit: Log out using: kill -9 $$

To Manually Clear your history: Type: history –c

Reverse-Search-History (reverse-i-search):

• Ctrl-r
• Note: Esc to exit, Enter to execute

To Search History Forward

• edit ~/.inputrc (unless overridded w/ the env var $INPUTRC)
• "\C-f": history-search-backward
• "\C-g": history-search-forward
• Usage: type 1st few letters of a previous command, then press Ctrl-f/g until you find the command

To add Date and Time to bash History (bash > 3.0) for all users, edit /etc/profile (for individual users, edit the /etc/bashrc file):

• Ex: "582 Thu 10-16-2014 11:19:49am : history", to do this just add export HISTTIMEFORMAT="%a %m-%d-%Y %H:%M:%S%P : "
• To see the current History Time Format: echo $HISTTIMEFORMAT
• Format of date / time follows strftime, see here

Hostname / Machine Name

hostname

Update /etc/sysconfig/network to include: HOSTNAME=myserver.mydomain.com

Update /etc/hosts file to include: 192.168.1.1 myserver.mydomain.com myserver

Set hostname without rebooting: echo > /proc/sys/kernel/hostname

Verify hostname is set:

• uname –n
• hostname

RHEL 7: /etc/hostname or hostnamectl

HTML Redirect

Redirect Code:

• <META HTTP-EQUIV=”Refresh” CONTENT=”5; URL=http://www.mynewredirect.com”>
• 5 = Wait 5 seconds before redirecting
• URL = URL to redirect to
• Place this between <head> and </head> tags

IOSTAT (CPU and I/O Stats for Devices & Partitions)

Prints CPU and Device I/O status, per second and overall: iostat

Display 3 reports at 1 second intervals for device sda and all it’s partitions: iostat –p sda 1 3

Ipconfig

Ifconfig

• ifconfig eth0 199.106.9.100 netmask 255.255.240.0 broadcast 199.106.8.255
• ifconfig eth0 up / down
• Show all Up interfaces: ifconfig –u
• Show all Down interfaces: ifconfig –d
• List all interfaces: ifconfig –l

ISO – Make DVD .iso out of CDs (RHEL 5 – 5 CDs into 1 DVD)

Create top directory, you will need almost 3gb of space:

1. mkdir dvd

Create directories on which to mount the CD ISO images using loop device mounts:

2. mkdir rhel5{1,2,3,4,5} rhel5-docs

Make an ISO out of each CD, drop ISO in correct directory:

3. dd if=/dev/cdrom of=/dvd/rhel51/rhel51.iso
4. dd if=/dev/cdrom of=/dvd/rhel52/rhel52.iso
5. dd if=/dev/cdrom of=/dvd/rhel53/rhel53.iso
6. dd if=/dev/cdrom of=/dvd/rhel54/rhel54.iso
7. dd if=/dev/cdrom of=/dvd/rhel55/rhel55.iso

Mount the new ISO images using a loop device mount:

8. mount –o ro,loop /dvd/rhel51/rhel51.iso rhel51
9. mount –o ro,loop /dvd/rhel52/rhel52.iso rhel52
10. mount –o ro,loop /dvd/rhel53/rhel53.iso rhel53
11. mount –o ro,loop /dvd/rhel54/rhel54.iso rhel54
12. mount –o ro,loop /dvd/rhel55/rhel55.iso rhel55

Copy the isolinux directory and the .discinfo from CD 1 to the current directory (i.e. dvd):

13. cp –a rhel51/isolinux rhel51/.discinfo .

Edit the .discinfo file, replace forth line with 1-5, this will tell the .discinfo file that it’s looking at 5 CDs total:

14. vi .discinfo, change line 4 to read 1,2,3,4,5

This is key, or you’ll get errors with mkisofs:

15. rm isolinux/boot.cat, (if not, you will get an error about a null pointer having same rock ridge name boot.cat)

Create the DVD ISO Image (l for long filenames, J so windows can read the disc, -R for filenames, -v verbose, -V volume label):

16. mkisofs –l –J –R –v –V "RHEL5" –o redhatesdvd.iso –b isolinux/isolinux.bin –c isolinux/boot.cat –no-emul-boot –boot-load-size 4 –boot-info-table –m TRANS.TBL –x rhel51/.discinfo –x rhel51/isolinux –graft-points rhel51 .discinfo=.discinfo isolinux/=isolinux Server/=rhel52/Server Server/=rhel53/Server Server/=rhel54/Server Server/=rhel55/Server VT/=rhel55/VT docs/=rhel5-docs

Create the DVD ISO Image for Oracle Enterprise Linux 4.7:

1. mkisofs –l –J –R –v –V "OEL47" –o OEL47.iso –b isolinux/isolinux.bin –c isolinux/boot.cat –no-emul-boot –boot-load-size 4 –boot-info-table –m TRANS.TBL –x el1/.discinfo –x el1/isolinux –graft-points el1 .discinfo=.discinfo isolinux/=isolinux Enterprise/=el2/Enterprise Enterprise/=el3/Enterprise Enterprise/=el4/Enterprise Enterprise/=el5/Enterprise

Test Mount the new DVD ISO:

• mount –o loop myfile.iso /mnt/tmp

Burn the new DVD ISO with Nero and Install!

Links: http://www.mjmwired.net/resources/redhat8-dvd.html

Links: http://www.linuxquestions.org/questions/showthread.php?t=148702

Network Install Prep: http://www.redhat.com/docs//manuals/enterprise/RHEL-5-manual/Installation_Guide-en-US/s1-steps-network-installs-x86.html

ISO - Make a Backup of a DVD

DVD to .ISO: dd if=/dev/cdrom of=/path/dvd.iso status=progress

JAVA - Check Heap Size

Check heap size of a running process: jmap -heap <pid_of_tomcat_process>

Jobs – Background, Foreground, Killing

To background a process or job use the & after the command:

• nano myfile.txt &

To foreground a process or job use:

• fg <job number>
• fg w/o a number brings most recently backgrounded process to the foreground

To list jobs currently running use:

• jobs

To kill a job use – this will request the job shutdown and clean up it’s tmp files:

• kill %<job number>

Note: If you’ve started a process in the foreground and you decide later that you’d like to background it, you can use Ctrl-Z to stop the process and then use "%&" on the command line to restart the process in the background

Jumbo Frames

Test it out: ifconfig eth0 mtu 9000

Make it permanent:

>vi /etc/sysconfig/network-script/ifcfg-eth0
• Add: MTU=9000
• Restart Network: service network restart

Check the configured MTU via netstat: netstat -i

Check the MTU via ifconfig: ifconfig

To confirm the MTU used between two specific devices. Use ip command as follows:

• ip route get {IP-address}
• ex. ip route get 192.168.1.1

You may need to tune the application / network protocol such as NFS and SMB to take advantage of Jumbo Frames.

Add this to /etc/samba/smb.conf:

1. read size = 262140
2. max xmit = 262140
3. socket options = TCP_NODELY SO_SNDBUF=262140 SO_RCVBUF=262140

Note: This sped up jumbo frames from 30-40MB/sec to 60-70MB/sec

Kernels - Removing Old and Unused Kernels on CentOS

By default CentOS will keep last 5 kernels installed on your system. This behavior is defined by installonly_limit=5 line within /etc/yum.conf file

• List your current Kernel: uname -a

• List all the old Kernels: rpm -q kernel

• Remove all the old Kernels except the latest currently loaded Kernel: package-cleanup --oldkernels --count=1

Kill (terminate or signal a process)

Escalating Kills:

• kill PID
• kill 1435
• kill –INT 1435 (i.e. Kill -2)
• kill –HUP 1435 (i.e. Kill -1)
• kill –KILL 1435 (i.e. Kill -9)

Signals (a signal is what linux uses for sending information between processes or between the kernel and a process):

• 0 = NORMAL EXIT status
• 1 = SIGHUP (can be used to force a process to re-read it’s configuration files)
• 2 = SIGINT (ctrl-c like)
• 9 = SIGKILL (Asta-la-vista baby, don’t wait, die!)
• 15 = SIGTERM (Please will you exit now, as soon as you possibly can)
• Note: List all the signals: kill –l

To Kill a user (disconnect them), kill their shell process (ex. PID sshd: root@pts/0):

• ps wwaux | grep sshd
• kill PID

ldd – Print shared library dependencies

[root@myserver bin]# ldd uxwdog

If you have program libraries that are stored in different directories on the system other than /lib, you might need to add something like this to your .bashrc file:

• export LD_LIBRARY_PATH=/var/opt/sun/directory-server/lib/

List system PCI devices and all devices connected to them

lspci

Locale – Change your language locale, UTF-8 or not

If you see weird characters in your Shell client, check to see if your Linux locale is set to use en_US.UTF-8 and you can change it to en_US:

• See the current Locale: cat /etc/locale.conf OR localectl status
• Change Locale from en_US.UTF-8 to en_US: edit /etc/locale.conf OR localectl set-locale LANG=en_US

To fix Ubuntu Server Error via SSH: -bash: warning: setlocale: LC_ALL: cannot change locale (en_US)

• Edit the default locale: sudo vi /etc/default/locale and add the following:
•   LANGUAGE=en_US.UTF-8
•   LANG=en_US.UTF-8
•   LC_ALL=en_US.UTF-8
• Run these commands:
•   sudo locale-gen en_US.UTF-8
•   sudo dpkg-reconfigure locales

Login Shell – User Login Shell

List available shells:

• cat /etc/shells OR
• chsh –l

Change a user’s Login Shell:

• chsh <user_name> /bin/bash
• ex. chsh jdoe /bin/bash

LogWatch

LogWatch configuration file: /etc/log.d/logwatch.conf

View / Change the Services LogWatch monitors: /etc/log.d/conf/services/.conf

LogWatch runs under cron.daily: /etc/cron.daily/00-logwatch (/etc/log.d/scripts/logwatch.pl)

To change what time cron.daily (hourly / weekly / monthly) runs: vi /etc/crontab

Ls – List Directory Contents

ls –d win* = (DOS) dir win*.*

ls –lh = lists files w/ Bytes, K units

ls –F = Marks directories w/ trailing /, marks executables w/ trailing *, marks smbolic links w/ trailing @

ls –ld */ = Show only directories (keep color codings)

MCPAN

Reconfigure MCPAN:

• Start CPAN: perl –MCPAN –e shell
• Enter this command: o conf init

Configure Perl CPAN URL List:

• Enter the shell: perl –MCPAN –e shell
• View current URL list: o conf urllist
• Erase list: o conf urllist shift
• Add new http URL: o conf urllist push http://mirror.hiwaay.net/CPAN/
• Save changes: o conf commit

MDADM / MDSTAT

View the status of all multi disk arrays: cat /proc/mdstat

View the status of a multi disk array: mdadm –detail /dev/md0

Rebuid array after receiving error message: Kicking non-fresh sdc1 from array!:

• Ex. Errors showing in /var/log/messages:
Dec 6 20:48:25 nas kernel: md: md0 stopped
Dec 6 20:48:25 nas kernel: md: bind
Dec 6 20:48:25 nas kernel: md: bind
Dec 6 20:48:25 nas kernel: md: kicking non-fresh sdc1 from array!
Dec 6 20:48:25 nas kernel: md: unbind
Dec 6 20:48:25 nas kernel: md: export_rdev(sdc1)
Dec 6 20:48:25 nas kernel: md: raid1 personality registered for level 1
Dec 6 20:48:25 nas kernel: raid1: raid set md0 active with 1 out of 2 mirrors

This can happen after a power failure or UPS problem. Try adding the kicked disk back into the array. This will rebuild the mirror from the good disk. It will take time.

• mdadm /dev/md0 –add /dev/sdc1
• mdadm –detail /dev/md0 (Will give the status of the Mirror)
• cat /proc/mdstat (Will show progress and details of the Mirror rebuild)

Memory (Investigate Memory Usage)

To Investigate Memory Usage on a Linux system you can use a few different tools:

• top
• free –mt (shows in MB w/ Totals)
• cat /proc/meminfo
• ps –eo vsz,ooki,pid,user –sort vsz

Use Watch to monitor Memory and Highlight Differences: watch –d free –mt

• Buffers = cache raw disk (or other blockdevice) blocks (like smartdrive)
• Cached = page cache use for filesystem-level caching, swapping, this is the disk cache
• Note: there should be very little unused memory available, Linux will cache most of the free RAM and free it up when applications need it. This causes disk IO, etc. to be read from cache instead which speeds up the system. Linux will also swap out processes that have been idle for awhile and free up more RAM for cache or applications – they will be swapped back in when they are needed.
• Linux considers unused memory as wasted memory.

mkdir

Create a directory and sub-directories:

• mkdir -p fruit/{apple,pear,peach} # This will create fruit\apple, fruit\pear and fruit\peach directories.

Modules – Lists modules currently loaded into the kernel

lsmod

mod_rewrite – for Apache / Apache2

By default, Apache2 comes with mod_rewrite installed. To verify its existence, run:

• ls -l /etc/apache2/mods-available/r*

To enable and load mod_rewrite:

• sudo a2enmod rewrite
• Restart Apache: sudo service apache2 restart

To use it, in .htaccess to not dispaly .php extensions, add this to .htaccess file:

motd – How to change the Message of the Day

vi /etc/motd

Cool ASCII Art Generator: Link. Very useful for Linux logon banners using Font: small, Character Width: Default, Character height: Default.

Mount

Cause all the file systems mentioned in fstab to be mounted as indicated (except those w/ noauto):

• mount –a

Mount CD-ROM:

• Create Mount Point Locally: mkdir /mnt/mycdrom
• Mount it: mount –t iso9660 –o ro /dev/cdrom /mnt/mycdrom

Mount USB device:

• RHEL7: list all drive partitions and their UUIDs: lsblk -f
• Mount the USB Device:
  • find out if it’s recognized: lsusb or in tree form: lsusb -t
  • find out device name: dmesg | tail
  • Create mount point: mkdir /mnt/usb
  • Mount it: mount –t vfat /dev/uba1 /mnt/usb

Mount a SAMBA share on Linux:

• mount –t cifs –o username=<username> //t2.worldnet.net/<sharename> /mnt/oracle

Mounted Devices – Display what’s mounted

• This displays all mounted file systems, the fs type, read/write status, etc. SCSI drives are denoted by ‘sd’, IDE by ‘hd’
• cat /proc/mounts

UnMount: umount uba1

Note: /etc/fstab defines mountable file systems & devices on startup. Edit this to make the mount available on startup

• vfat file system is MS Windows w/ long filename support

MySQL Commands

• MySQL Complete
• SQL Crib Sheet

Show Databases:

Use a Database:

Show Database Tables:

Dump Database:

Log in as root & use the mysql DB:

Add Users:

Show mysql Users:

Create new Database:

Import Database SQL Dump into new DB:

Remove all Records from a Table:

Remove a Table:

Count Records:

Alter: Add a Column to a Table:

Select: Select from 2 Tables:

Show Version and Proc:

MySQL Help, List Server-Side Help:

Name Resolution - Configure

/etc/hosts

/etc/resolv.conf

netstat - network connections, routing tables, interface stats, etc.

Show Listening Ports and Processess, numerically (i.e. not by service name):

• netstat -nl

Show only Listening TCP sockets::

• netstat -nlt

Show only Listening UDP sockets::

• netstat -nlu

Show only Listening UNIX domain sockets::

• netstat -nlx

Note: netstat translates the default ports to the service name using the mappings from this file: /etc/services

Network Card Configuration via Command Line

Server Side, Edit /etc/sysconfig/network-scripts/ifcfg-eth0:

• Note: ONBOOT=YES or NO
• Note: IPADDR, NETMASK, GATEWAY

Save file and then: service network restart

NFS

Server Side, Start NFS:

• /sbin/service nfs status
• /sbin/service nfs start/stop/reload
• /sbin/chkconfig –level 345 nfs on

Server Side, edit: /etc/exports

• directory hostname(options)
• /homes slab2.abc.com(rwx,sync)
• /homes *.abc.com(rwx,sync)

Server Side, Notify NFS daemon of your change: /sbin/service nfs reload

Client Side:

• Client Side, Create mount point directory: mkdir /homes
• Client Side, Mount NFS directory: mount server:/homes /homes
• Client Side, Mount NFS via fstab: server:/homes /homes nfs rsize=8192,wsize=8192,timeo=14,intr
• Client Side, Mount NFS via autofs: use /etc/auto.master, /etc/auto.misc, etc.

Note: exportfs –a exports all directories in /etc/export

Note: exportfs –au un-exports all directories in /etc/export

NFS: Locking Down the Ports, Opening the Firewall - How can I configure a system as an NFS server which sits behind a firewall with NFS clients outside of the firewall?

Server Side, Create or Edit /etc/sysconfig/nfs:

Server Side (may not need this): reboot

Server Side, Check the Port Assignments: rpcinfo –p localhost

Server Side, Open these Ports in the Local Firewall:

NFS Troubleshooting

Server-Side:

• Display NFS Activity: nfsstat –s
• Display all remote mounts: showmount –a
• Display only the names of the directories mounted by the clients: showmount –d
• Display list of the file systems exported by the server: showmount –e

Client-Side:

• Display information on the file systems mounted remotely, mount point, amount of available space: df –hF nfs
• Display NFS activity on Client: nfsstat –c

NetworkManager on CentOS / RHEL 7.x

Service

• Display service information: systemctl status NetworkManager
• Enable service at Boot: systemctl enable NetworkManager
• Disable service at Boot: systemctl disable NetworkManager
• Service other: systemctl start|stop|restart NetworkManager

Common Commands:

• Display General Network Status: nmcli general status
• Display List of NetworkManager-recognized Devices and their current Status: nmcli device status
• Display Device Connection Status: nmcli con show
• Display Detailed Device and Connection Information: nmcli device show
• Disconnect a Device (ex. ifconfig eth0 down): nmcli device disconnect ens32
• Connect a Device (ex. ifconfig eth0 up): nmcli device connect ens32

NTP Server Setup (UDP 123)

Setting up Linux as a Time Server:

1. Install latest version of ntp (rpm –qa | grep ntp)
2. Edit /etc/sysconfig/iptables add upd access for port 123 (ntp)
3. Make sure Service Starts on boot in current runlevel: chkconfig ntpd on
4. Modify /etc/ntp.conf (add time servers, add restrictions for local network access)
5. ntpdate –b pool.ntp.org (initial sync, done the first time before ooking the daemon, do NOT need to do each time the daemon starts)
6. Start Service: service ntpd start
7. Verify it’s running: pgrep ntpd
8. Verify it’s listening: netstat –tuna
9. Check how it’s synchronized: ntpq –p

Indication That Your Time Server is Working:

• The delay and offset values should NOT be 0 and the Jitter values should be under 100

Telltale Sign Your Server is Not Synchronizing:

• All remote servers have jitters of 4000 w/ delay and reach values of 0

Note: Your internal workstation computers will not be able to use the server as a synchronization source until the LOCAL(0) clock has stable time. This may take up to 15 minutes after starting the NTP daemon

Time Servers:

Working Configuration File: ntp.conf

NTP Server Tools

It may take a number of minutes for the clock to synchronize. You can use the ntpdc command to view information about ntpd’s status. It can be used in interactive mode, by simply entering ntpdc, or invoked with the –c switch to run the commands from the shell prompt.

Note: these commands will only work on a server running ntpd, i.e. a Time Server, not a Client

Here is a list of useful ntpdc commands:

• ntpdc –c listpeers (list known peers)
• ntpdc –c peers (list known peers & their state summary)
• ntpdc –c sysinfo
• ntpdc –c sysstats (print stats counters maintained in the protocol module)
• ntpdc –c iostats (print stats counters maintained in the input-output module)

Oracle

Get Oracle Version Number: select banner from v$version;

OS / Kernel Version

uname –sr = kernel name, kernel release

uname –r = kernel release number

uname –v = kernel version

cat /etc/xxxxx-release = where xxxxx is redhat, fedora, etc. this shows what OS and version is installed

Pam.d (Auto-create Home Directories on a Server when Logging in using LDAP authentication)

Each client is responsible thru pam.d to create their own home folder when they log in to a server using ldap.

Make sure each client uses authconfig to use the LDAP server (use MD5 passwords, Use Shadow Passwords, Use LDAP Authentication, Local authorization is sufficient)

When the client logs in, the client pam uses the ldap attribute called: homedirectory as the path to create their home directory.

To enable the client to create their home directory based on that ldap attribute, you add this line to: /etc/pam.d/system-auth:

• session required /lib/security/$ISA/pam_mkhomedir.so skel=/etc/skel
• Note: you can add this to the end to auto-set the umask: umask=0077 (Which gives 700 to the home directory)

Here’s the Step by Step along with setting up permissions ACL on the home directory: Document

Password – change users password

passwd username

Lock a User Account: passwd –l username

Unlock a User Account: passwd –u username

Set User Account Expiration: usermod –e 07/23/2006 username

Path, Setting your Path

export PATH=$PATH:/my/new/directory1/:/two

Enter this each time you login or add to your .bashrc file so it will stick on subsequent logins

Adding a ‘.’ As the last entry in the PATH means current directory for a program name. Thus preventing you from having to type ‘./myprogram’ to execute a program. Just type ‘myprogram’

Perl – Installing Modules

Manual Way:

1. Download perl-ldap from cpan
2. gunzip –c perl-ldap-0.29.tar.gz |tar xvf –
3. cd perl-ldap-0.29
4. perl Makefile.PL
5. make
6. make install

Easy Way:

1. perl –MCPAN –e ‘install Net::LDAP’

Perl – Check for Existence of a Perl Module on your System

Does a Module Exist:

• An easy way to check for the existence of a Perl module on your system (technically, in Perl’s @INC array, a list of directories Perl searches when attempting to load modules) is to run perl –e ‘use module;’
• Example: perl –e ‘use HTML::Parser;’
• If nothing is returned, Perl was able to locate the module. Otherwise, you will see Can’t locate HTML/Parser.pm in @INC.

View @INC array (to see where Perl is searching for it’s modules): perl –V

Permissions

User / Owner (you)

Group (a group of other users that you set up)

Other / World (anyone else browsing on the file system)

The value of each digit is set according to what rights each of the types of people above have to manipulate that file.

Permissions are set according to numbers. Read is 4. Write is 2. Execute is 1. The sums of these numbers give combinations of these permissions:

• 0 = no permissions; person cannot read, write, or execute the file
• 1 = execute only
• 2 = write only
• 3 = write and execute (1+2)
• 4 = read only
• 5 = read and execute (4+1)
• 6 = read and write (4+2)
• 7 = read and write and execute (4+2+1)

Ex. chmod 700 myfileonly.html

Permissions: Change the group of a file:

• chgrp <newgroup> <filename>
• Change Group to <gName> in this Folder Recursively: chgrp –R <gName> .

Permissions: Change the owner of a file:

• chown <newuser> <filename>

PGREP – Show Process ID

pgrep looks through currently running processes & lists the PID’s which match the selection criteria

• pgrep smb / pgrep oracle

PHP – php.ini

vi /etc/php.ini

Postfix

Postfix mail system commands below are reserved for superuser / root users only.

sudo postfix reload (Re-read configuration files, Running processes terminate at earliest convienence)

sudo postfix status (Indicates if postfix is running, if so its PID)

sudo postfix stop (Stops postfix in an orderly fashion)

sudo postfix start (Starts postfix and runs a configuration check)

sudo systemctl restart postfix (Restarts postfix using systemctl)

sudo postfix check (Runs a configuration check)

Note: Postfix configuration files are: /etc/postfix/main.cf and /etc/postfix/master.cf

Power Off / Shutdown / Reboot

poweroff (turns off computer)

shutdown –r now (reboots)

reboot (reboots)

Print Screen (PrtScn) – in X

Capture the entire screen: press "PrtScn" button

Capture where Mouse points to: press "Alt+PrtScn" button

Process Status

ps

Processes – Show

ps –A –-sort command / cmd, Ex. ps -A --sort=uid,cmd or ps -A --sort=pid

ps –A | grep httpd

ps –wwaux

Show in Tree Form: pstree

Return to Your Home Directory

cd ~

Root Password, Forgot Root Password

http://www.creativelogichome.com/unix/unixrpw.htm

Route – Adding / Deleting

Add a Static Route to the 10.199.1.0 Network Using the Gateway of 192.54.86.51:

• route add –net 10.199.1.0 netmask 255.255.255.0 gw 192.54.86.51

Delete that Static Route to the 10.199.1.0 Network Using the Gateway of 192.54.86.51:

• route del –net 10.199.1.0 netmask 255.255.255.0 gw 192.54.86.51

Show the Current Routes:

• route –v

Note: To Make the Routes Permanent (so they stick when the box is rebooted):

• add the "route add" command(s) to the bottom of /etc/rc.local file

Routing Table, Display Kernel IP Routing Table

netstat –nr

route –v

RPM

Query version of a package:

• rpm –q <package>
• ex. rpm –q kernel (displays installed kernels)

Install a package:

• rpm –ivh <package>

Force Install of package:

• rpm –ivh -force <package>

List contents of a package (shows files and file destination paths):

• rpm –q –filesbypkg –p <package>
• rpm –qpl <package>

Remove / Erase a package:

• rpm –e <package>

Show all installed packages:

• rpm –qa

Show where package was installed (ex. Pine):

• rpm –ql pine

Following command can be used to distinguish between a 32-it or 64-bit package:

• rpm –qa –queryformat "%{NAME}-%{VERSION}-%{RELEASE} (%{ARCH})\n" | grep libaio-0.3

RSYNC – backup

rsync –av source/ destination/

• Trailing slash on the source matters, if omitted, produces destination/source/<files>

rsync -av --delete source/ destination/

• --delete deletes any file from destination/ that is not in source/ any longer.
• By default if a file is deleted from source/ and had already been rsync’d to destination/ the copy in destination/ will not be removed

rsync –n –av –delete source/ destination/

• The –n command will do nothing but display what rsync *would* do

Switches:

• --stats gives some file-transfer statistics
• --exclude ‘*.txt’ will exclude all .txt files
• --progress shows progress during transfer
• --exclude-from ‘/home/backup/exclude.txt’ excludes all files listed in exclude.txt, ex:
  • myBadDirectory
  • public_html/database.*
  • downloads/*

Run Levels - (Runlevel)

Ctrl-Alt-F1 = switch to console

• init 1 = console / single user
• init 3 = full multiuser, stops X server
• init 5 = Start X server, X11
• cat /etc/inittab = displays runlevels in file
• change default run level /etc/inittab, line: id:5:initdefault:

RHEL / CentOS 7:

• systemctl get-default = Check your current runlevel settings
  • If current setting is: graphical.target then Linux will boot into GUI Mode
  • If current setting is: multi-user.target then Linux will boot into NON-GUI Mode

• systemctl set-default multi-user.target = After this command and a reboot, Linux will book into Non-GUI (ex. init 3) runlevel

Running Remote X Applications

On local machine, log into GUI, open terminal window:

• ssh –X blah@xxx.xxx.xxx.xxx to securely run remote x applications

echo $DISPLAY to see what display is being exported

Run remote X Applications – Export Display

On local machine:

• Start xterm
• xhost remote.machine.ip

On Remote Machine:

• export DISPLAY=local.machine.ip:0

Samba

List info about machines that respond to SMB name queries on a subnet. Use this to see if your local host smb is started.

• findsmb

Connect to Samba Share:

• smbclient //192.168.1.1/<sharename> - U <username>

List Local Samba Shares (w/o password):

• mbclient –L localhost –N

Create a samba password:

• On the samba server: smbpasswd –a <username>

Samba configuration file:

• /etc/samba/smb.conf

Scheduling Jobs

at <time> = runs commands at specified time

atq = lists pending commands

atrm <job> = cancels pending jobs

batch = runs commands when system load permits

SCP (Secure Copy) – Remote File Copy, uses SSH

scp –P <target port> <file1> <user@host>:<location on host>

Ex. scp –P 42XXX myfile.tar.bz2 uers@remotesystem.worldnet.net:/home/oracle

Copy an entire Directory (all files below, recusively (-r) AND preserve modification times (-p)) to a Target system directory (If target directory doesn't exist, it will be created (-r)):

• scp -rp localFolderAndFilesWithin/ user@remoteserver.org:/remoteFolder/
• Note: This will copy all the contents to: /remoteFolder/localFolderAndFilesWithin/

Copy a file From a Remote Server to Your Local Server

• scp user@remoteserver.org:/file/to/copy.txt /local/system/copy/

Screen – Screen Manager w/ VT100 / ANSI Terminal Emulation

Install: yum install screen

Screen Commands from within the Root Terminal:

• Start: screen
• Start using a session_name: screen -S myname
• Attach to a Screen: screen -r <session_name> OR <session_ID>
• Reattach to a single Screen Session: screen -r
• -- If you try to reattach and you get get an error about no screens to attach to, first detach, then reattach: screen -d -r <session_name>
• Force Detach the Screen: screen -x -R
• Create and Name a screen Session: screen -S <session_name>
• Create and Name a Screen Session and Name the Terminal: screen -S <session_name/ID> -t <terminal_name>
• Kill / Quit a Screen Session using Name: screen -S <session_name> -X quit
• List Screens: screen -list OR screen -ls
• Set a Title for your Screen session: screen -t <title>
• To Join a Screen that is already attached (ex. for training / shadowing): screen -x <session_name/ID>
• How to tell if you are in a Screen Session: Ctrl-a t

Screen Commands from within a Screen Session:

• Name your Screen Session: Ctrl-a : sessionname myname
• Create a new Window: Ctrl-a c
• Exit the current Window / Session: exit
• Kill the current Window / Session: Ctrl-a k
• Kill current and All Sessions: Ctrl-a \
• Lock your Screen Session: Ctrl-a x
• Switching between Windows: Ctrl-a n
• Switching between Current and Previous Windows: Ctrl-a Ctrl-a
• Detach from a Screen Session: Ctrl-a d
• List Screens: screen -list OR screen -ls
• Logging your Screen Output: Ctrl-a H
• Set ACTIVITY alert for a window: Ctrl-a M
• Set INACTIVITY alert for a window: Ctrl-a _
• Show Status Bar: Ctrl-a w

Screen Scrollback Buffer:

• Increase Screen scrollback buffer while in a screen: Ctrl+A : then type: scrollback 10000
• -- to scroll while in a screen: Ctrl+A ESC then type use the mouse wheel to scroll. To exit scrolling mode press:ESC

Script – Make a typescript of a terminal session

This command makes a typescript of everything printed on your terminal:

• script
• Note: To Exit: Ctrl-D

Search through files to find text (fgrep)

fgrep "search_word" *.*

fgrep = grep –F

Sed – Search and Replace within Files (ex. *.html)

This command will search all .html files and replace 'foo' with 'bar'

• sed –i 's/foo/bar/g' *.html
• Note: Before you run this command make sure grep returns what you expect: grep "foo" *.html

If you want to get sed to make a copy of the original file prior to the change do:

• sed –i.bak 's/foo/bar/g' *.html
• Note: each backup will be named *.html.bak

Sendmail

Make changes to the /etc/mail/sendmail.mc file, then compile with:

• m4 sendmail.mc > sendmail.cf

If you get this error: "sendmail.mc:10: m4: Cannot open /usr/share/sendmail-cf/m4/cf.m4: No such file or directory", then:

• Install sendmail-cf using: yum install sendmail-cf

Send Mail from the Command Line:

• usr/sbin/sendmail –t
• To: sysadmins@mydiego.edu
• From: ocsinfra@mydiego.edu
• Subject: OCSINFRA: Gone to Heaven
• The CPU Load on OCSINFRA has caused a FATALITY. OCSINFRA is now D.E.A.D and has Gone to Heaven
• .

..OR..

• sendmail –v user@domainname < test.mail
• Where test.mail has:
Subject: test mail
first line of my message
[blank line]

Sendmail - Configure to Send Outgoing Messages

/etc/hosts file: xxx.xxx.xxx.xxx mail_hostname

/etc/mail/sendmail.mc file: define(`SMART_HOST',`mail_hostname')

Recompile sendmail.mc: m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

Restart sendmail: service sendmail restart

Add this line to /etc/hosts.allow: sendmail : localhost : ALLOW

How To:

• Check Sendmail Process: ps -ef | grep sendmail
• How to see the mail queue: mailq
• Monitoriing Sendmail Log Activity: tailf /var/log/maillog
• Sendmail Log Rotation: vi /etc/logrotate.d/syslog

SELinux

Check SELinux Status:

• sestatus

Disable SELinux:

• vi /etc/sysconfig/selinux
• Change line to: SELINUX=disabled

Note: If you changed from Enabled to Disabled or vice versa, you need to restart the machine for the change to take effect.

Services

Apache = httpd

DHCP Client = dhclient

DNS Server = named

Firewall = iptables

• iptables –list
• service iptables status = shows rules

Services – updates and queries runlevel information for system services

chkconfig

List which services are available and in which runlevel they are started:

• chkconfig –-list

Update:

• Ex. chkconfig –-level 3 smb on|off|reset

List all services that are turned on in runlevel 5:

• chkconfig –-list | grep ‘5:on’ | sort

Delete / Remove a service from chkconfig management and any symbolic links in /etc/rc[0-6].d which pertain to it are removed:

• chkconfig –-del <service_name>

Text GUI for managing which services are started in the current runlevel, can use the –level to modify other runlevels:

• ntsysv

Services, Start, Stop, Restart

service <service_name> start|stop|restart

• Ex. service httpd restart

To check the Status of a Service:

• service httpd status

RHEL 7 / CentOS 7:

• Get the Status: systemctl status xxxxx.service | xxxxx
  • Ex. systemctl status network.service or systemctl status network
• Restart the Service: systemctl restart xxxxx.service | xxxxx
• Start the Service: systemctl start xxxxx.service | xxxxx
• Stop the Service: systemctl stop xxxxx.service | xxxxx

SFTP (Secure File Transfer Program)

To open a secure, interactive FTP session that is encrypted: sftp user@server.com

Once authenticated, use regular FTP commands

Shell Commands: Bash, Bash Command Line Editing Commands

Bash readline:

• Move to Beginning of Line: Ctrl-a
• Move to End of Line: Ctrl-e
• Move Backward a word: Esc b
• Move Forward a Word: Esc f
• Move Backward a Character: Ctrl-b
• Move Forward a Character: Ctrl-f
• Clear the Screen, reprint the current line at the top: Ctrl-l
• Delete / Kill the text from the current cursor position to the End of the Line: Ctrl-k
• Delete / Kill backward from cursor to Beginning of the line: Ctrl-u
• Move to Previous History Command (up): Ctrl-p
• Move to Next History Command (down): Ctrl-n
• Reverse Search History (up): Ctrl-r
• Forward Search History (down): Ctrl-s
• Display your Shell Version: Ctrl-x, Ctrl-v
• Repeat last command: !!
• Terminate the command: Ctrl-c
• Delete from under the cursor: Ctrl-d
• Backspace: Ctrl-h
• Search the history backwards with multi occurrence: Ctrl-R
• Swaps last two chars in line: Ctrl-t
• Delete last word in line: Ctrl-wli>
• Move between BOL and current cursor position: Ctrl-xx
• Show possible hostname completions: Ctrl-x @
• Paste what you Cut (ctrl-k): Ctrl-y
• Suspend/ Stop the command: Ctrl-z
• Scroll Screen Up: Ctrl-PageUp
• Scroll Screen Down: Ctrl-PageDn
• Scroll Screen Up, by Line: Shift-PageUp
• Scroll Screen Down, by Line: Shift-PageDn

To Enable VI style Key Bindings: set –o vi, press Esc to activate VI style Editing

To Enable Emacs Bindings (default): set –o emacs

To list all Bindings: bind –p

Single User Mode

Edit Kernel line, add "single" at the end, boot the modified kernel line. In GRUB:

• 'e'
• select kernel line, press 'e'
• add single, ' single' at EOL
• ENTER
• 'b' to boot it

smartctl

Verify the manufacturer, model, and SMART capability, and look at the current state of health (as last recorded):

• smartctl –ia /dev/sda
• See Error Logs

SSH - Change Terminal Title

To have your hosting provider set your linux terminal title to username@host:directory, add this to your hosted accounts ~/.bashrc:

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
    ;;
esac

• Last tested on Ubuntu Mate 20.04

SSH (OpenSSH Remote Login Client)

To execute a command on a remote machine without logging into a shell prompt:

• ssh user@server.com ls /var/log

Use your OpenSSH Private Key to Login to a Server that has your Public Key (default is ~/.ssh/id_rsa):

• ssh -i /path/to/id_rsa-private-key user@server.com

SSH (Generating Authorization Key Pairs)

Starting with OpenSSH 3.0, SSH protocol 1 and 2 share these files:

• ~/.ssh/authorized_keys
• ~/.ssh/known_hosts
• /etc/ssh/ssh_known_hosts
• Note: If you want to reinstall Linux and save your generated key pairs, backup the .ssh directory in all users homes folders, reinstall, copy the directories back

Starting with OpenSSH 2.9, the default keygen uses RSA

Note: A passphrase is a string of words and characters used to authenticate a user. Passphrases differ from passwords in that you can use spaces or tabs in the passphrase. Passphrases are generally longer than passwords because they are usually phrases instead of a single word.

Generating Authorization Key Pairs – prevents having to use password each time you ssh, scp, or sftp into a remote machine

Keys MUST be generated for each user. Follow these steps as the user who wants to connect to a remote machine (for ex. If you complete these steps as root, only root will be able to use the keys):

Client (source) Machine:

• Run: ssh-keygen -b 2048 –t rsa
• Save the key to default location
• Enter passphrase, or blank for none
• Re-enter passphrase
• NOTE: The public key is now located in ~/.ssh/id_rsa.pub.  The private key (identification) is now located in ~/.ssh/id_rsa
• Copy the contents of ~/.ssh/id_rsa.pub (your public key) to ~/.ssh/authorized_keys on the remote (destination) machine you want to connect to. If authorized_keys doesn’t exist, create it.
  • Ex. ssh-copy-id user@123.45.56.78
  • OR cat id_rsa.pub >> /root/.ssh/authorized_keys

General Process: Generate keys on the Client, Copy the client .pub key to the desired user (their .ssh/authorized_keys file) who you want to connect as on the remote server

• After generating keys, you can delete .ssh/id_rsa.pub on the client, but you cannot delete the private key (id_rsa) on the client, if you do, you cannot authenticate keylessly. If you want a different local / client user to be able to login to the remote server (as that same remote user), you can copy the other users private key to the new users .ssh/id_rsa file. Not advised though.

Using the Keys:

• Specify a different private key to login to a server that has your public key: ssh -i /path/to/id_rsa-private-key user@server.com

Getting / Comparing the Public Key from the Private Key:

• This command reads the Private Key and print the Public Key: ssh-keygen -yf /path/to/id_rsa-private-key

SSH Terminal Character Encoding

If you see characters such as: †in your SSH session, it's the terminal program's character encoding that neets to be set to UTF-8

• In PuTTY check in: Settings -> Window -> Translation
• In SecureCRT check in: Session Options -> Terminal -> Appearance -> Character encoding

SSH Daemon – sshd

Disable direct ssh Root login:

• Add: PermitRootLogin no to /etc/ssh/sshd_config
• restart sshd

Check SSL Certificate Expiration Date:

echo | openssl s_client -connect hostname.xxx.xxx:port 2>/dev/null | openssl x509 -noout -dates

Dump SSL Certificate Data:

openssl s_client -showcerts -connect hostname.xxx.xxx:port

Startup – Xwindows (Windows Startup Folder Equivalent)

To start a script or program when the user logs on using startx (KDE / GNOME) place a script here:

• /etc/X11/xinit/xinitrc.d

Ex. To Start Synergy client:

• Create synergy.sh script:
• #!/bin/sh
• /usr/bin/synergyc –daemon <server>
• chmod 755 synergy.sh
• Reboot and enjoy!

SUDO

Config File is: /etc/sudoers

Edit the Config File using visudo

• visudo uses editor stored in environment var VISUAL, can set using: export VISUAL=”pico –w”)

• To change visudo editor from nano to vim, type: sudo update-alternatives --config editor) on Ubuntu / Raspberry Pi, etc.

Create User Groups under “User Alias Specification” section:

• User_Alias ADMINS = ,

Give Groups permissions in “User Privilege Specification” section:

• %ADMINS ALL=(ALL) ALL

Execute command as user (use users pass): sudo vi /etc/sudoers

Swap File Usage

To monitor Swap Space Usage: swapon –s

..or..: cat /proc/swaps

Syslog

To disable /var/log/messages output

• vi /etc/syslog.conf – look for line next to /var/log/messages and comment it out
• service syslog restart – for changes to take effect

SystemD

System Service Management, using the systemctl action service pattern:

• systemctl start <service> - Use it to start a service. Does not persist after reboot
• systemctl stop <service> - Use it to stop a service. Does not persist after reboot
• systemctl restart <service> - Use it to restart a service
• systemctl reload <service> - If the service supports it, it will reload the config files related to it w/o interrupting any process that is using the service
• systemctl status <service> - Shows the status of a service. Tells whether a service is currently running
• systemctl enable <service> - Turns the service on, on the next reboot or on the next start event. It persists after reboot
• systemctl disable <service> - Turns the service off on the next reboot or on the next stop event. It persists after reboot
• systemctl is-enabled <service> - Check if a service is currently configured to start or not on the next reboot
• systemctl is-active <service> - Check if a service is currently active
• systemctl show <service> - Show all the information about the service
• sudo systemctl mask <service> - Completely disable a service by linking it to /dev/null; you cannot start the service manually or enable the service
• sudo systemctl unmask <service> - Removes the link to /dev/null and restores the ability to enable and or manually start the service

Note: Systemd provides a standard process for controlling what programs run when a Linux system boots up. While systemd is compatible with SysV and Linux Standard Base (LSB) init scripts, systemd is meant to be a drop-in replacement for these older ways of getting a Linux system running. Systemd, which was created by Red Hat's Lennart Poettering and Kay Sievers, does more than start the core programs running. It also starts a journal of system activity, the network stack, a cron-style job scheduler, user logins, and many other jobs. That may sound good to you, but some developers hate it.

System Uptime

uptime

Tail

Outputs the last part of files

-f = output appended data as the file grows; follow output

Ex. tail –f /var/dhcpd/dhcpd.leases

Tar / Archiving Files

Tar:

• NOTE: By default, tar will preserve file permissions and ownership when creating the archive. To extract file permissions and ownership, you will need to run tar as root when extracting, since changing file ownership usually requires superuser privileges.


• Compress a tar/gzipped archive: tar –czvf archive.tar.gz files
• Decompress a tar/gzipped archive: tar –xzvf archive.tar.gz - this filters .tar through gzip first
• Ex. tar –cvf mej.tar *.doc where cvf = create verbose file

Tar a Directory:

• move to a superior (parent) directory: tar -cvf mej.tar mydirectory
• To exclude a folder: tar --exclude mydirectory/logs -cvf mej.tar mydirectory
• To exclude a file pattern: tar --exclude=*.log.gz -czvf shib4x.tar.gz shibboleth-idp

UnTar:

• Extract an entire archive in current directory: tar –xvf mej.tar
  • xvf = extract verbose file
• Extract specific files in archive: tar –xvf mej.tar 2.doc
• Extract specific directories in an archive (ex. Mydir1 inside of mydir):
  • tar –xvvf mej.tar mydir/mydir1
• Extract the archive but strip leading path. Ex. archive begins with /public_html/myfiles/.. will produce myfiles/…
• tar -–strip-components=1 –xzvf mej.tar.gz

Append / Add files to Tar:

• tar –rvf mej.tar 5.doc where rvf = append verbose file

List Files in Tar:

• tar –tvf mej.tar where tvf = list verbose file

Backup: Compare contents of a .tar with your backup directory:

• tar –fd myhomebackupdir.tar /home/*

Backup: Easily add files not found in your backup .tar to the .tar:

• tar –rvf myhomebackupdir.tar /home/*

Tar Pipe

cd <source_directory>

• tar cvf - . | (cd /<target_directory> ; tar xvf -)

Tar Pipe w/ Exclude File:

• cd <source_directory>
• create exclude.lst file to hold files / directories to exclude from taring
• echo "./mydir" or "./.myhiddendir" > exclude.lst
• create target_directory
• from the source_directory:
  • tar cXvf exclude.lst - . | (cd /target_directory ; tar xvf -)
  • Note: switch order matters!

Terminal Type (Checking your Terminal)

echo $TERM

Note: PuTTY uses: xterm, while others use ansi

Terminal Colors (SSH)

Change the Dark Blue directory color (XTERM color):

• vi /etc/DIR_COLORS (Search for #directory and change DIR 01;34 to DIR 01;33 (for yellow instead of blue)
• Attribute Colors: 00=none 01=bold 04=underscore 05=blink 07=reverse 08=concealed
• Background Colors: 40=black 41=red 42=green 43=yellow 44=blue 45=magenta 46=cyan 47=white
• Text Colors: 30=black 31=red 32=green 33=yellow 34=blue 35=magenta 36=cyan 37=white
• Examples: .tar 47;35 (magenta text on white background) DIR 00;33 (bright/bold yellow)

Note: then logoff and logon again. If that doesn’t work, also edit: /etc/DIR_COLORS.xterm and try again

Text File Conversions (Unix to Windows, Windows to Unix)

Convert a text file from Windows/DOS to UNIX:

• tr –d '\015' < winformat.txt > unixformat.txt

Convert a text file from UNIX to Windows/DOS:

• sed –d 's/$/\r/' unixformat.txt > winformat.txt

Time (Benchmarking tool)

Runs the specified program command with arguments and upon finishing, time writes a message to STDOUT giving timing statistics about the program.

1. Prints the elapsed real time between invocation & termination

2. Prints the user CPU time

3. Prints the system CPU time

time traceroute www.google.com

• traceroute to www.google.com (64.233.187.103), 30 hops max, 60 byte packets
• ...
• ...
• real 0m13.796s
  user 0m0.004s
  sys 0m0.008s

Time Server – Manually set the host clock via time server

ntpdate time.windows.com

Query TS, doesn’t set clock: ntpdate –q <timeserver>

Query the hosts CMOS clock: hwclock –show

Top – Display Linux Tasks

To sort by CPU (or other Field): Shift+f (or Shift+o), then K for %CPU, P makes Top order by CPU, W saves the configuration

Note: in RHEL 7 (procps-ng version 3.3.10), you can use the arrow keys to choose sort fields when in field management mode.

When Viewing Top in RHEL 7:

• Arrow Up / Down: Moves the process list up or down
• Arrow Left / Right: Moves the process columns left or right

Users

users = list current users

who = displays who is on the system

w = displays who is on the system and what they are doing

last = indicates last logins of users and ttys

Undo typing in shell / terminal (deletes entire line)

Ctrl-u

Uniq – Unique

Removing Duplicate Lines with: uniq

• cat <filewithduplicates> | uniq

Display only the Unique Lines

• cat <filewithduplicates> | uniq -u

Display only the Duplicate Lines

• cat <filewithduplicates> | uniq -d

Display Number (count) of Unique Lines

• cat <filewithduplicates> | uniq –uc

Display Number (count) of Duplicate Lines

• cat <filewithduplicates> | uniq –dc

Display Unique Lines in messages, skip field 3 (i.e. ignore unique timestamp field)

• uniq –f 3 /var/log/messages

Display Unique Lines in messages, skip field 3 and 9 more characters from there (i.e. ignore unique timestamp field + 9 characters)

• uniq –f 3 –s 9 /var/log/messages

User Administration (Add / Delete / Modify / Change password / Switch)

Add a new user: useradd

• –c Add a comment (any string for a short description of the login, ex. Full Name of user)
• –d home directory
• –s starting shell / program
• –p password
• –g primary group assigned to the user
• –G other groups the user belongs to
• –m create the user’s home directory
• ex. useradd –m –c "Homer Simpson" hsimpson -p Password
• ex. useradd –gusers –Gmgmt –s/bin/ –pxxxx –d/home/roger –m roger

Modify a user: usermod

• -a (append) –d (homedir), -s (login shell), -p (password), -g (initial login group), -G (supplementary groups)
• ex. usermod –G others roger
• Add user to the sudo group: usermod –aG sudo roger

Rename a user: usermod –l

• ex. usermod –l <newUsername> <oldUsername>

Delete a user: userdel

• –r remove home directory
• ex. userdel –r roger

User’s password: passwd

• option: user’s name
• ex. passwd roger

Force User to Change Password at Next Login:

• ex. chage –d 0 hsimpson

Switch to a Users: su

• ex. su roger

Add a group: groupadd

• ex. groupadd oinstall

Delete a group: groupdel

• ex. groupdel oinstall

User / Group File Information:

• User names and primary groups are stored in /etc/passwd
• Passwords for each user is stored in /etc/shadow
  • only edit this file by using the passwd command
• Group information is stored in /etc/group
• When a new user is created, the default files and directories that are created are stored in /etc/skel
  • You can modify this directory to fit your needs
  • Modifications only affect new users

Vi (vim) – text editor

VIM Complete

Hilight / Visual Mode:

• Cut = c (c$ to end of line)
• Copy = y (y$ to end of line)
• Paste = p (P = before cursor)
• Delete = d (d$ to end of line)
• V = visual Line mode
• Ctrl-V = visual Block mode

As you Type in Insert Mode:

• Back Space / Erase = Ctrl-H
• Line Kill = Ctrl-U
• Word Kill = Ctrl-W

Insert Mode:

• a = Append, moves cursor 1 position right before inserting (A = appends at end of line)
• o = Inserts a blank line under (O = above) current cursor position

Command Mode:

• Delete Everything from your current line to end: dG
• Delete Everything from your current line to the TOP of the file: dgg
• Delete a Character = x
• Delete a Word = dw
• Delete a Line = dd
• Undo a command = u
• Save the current file As another file, and begin editing that file = :sav <another_file>
• Save the current file contents to another file, continuing editing current file = :w <another_file>
• Save certain lines = :1,10w stuff.txt
• Status line = :f or Ctrl-G
• Move to Beginning of File (BOF) = 1G
• Move to End of File (EOF) = G
• Move to top of screen = H
• Move to middle of screen = M
• Move to lower portion of screen = L
• Move forward (down) a page = Ctrl-F
• Move backward (up) a page = Ctrl-B
• Move to Beg of Line = 0 (zero)
• Move to End of Line = $
• Move to First Line of the file = 1G
• Move to Last Line of the File = G
• Move to Line 10 = :10 or 10G
• Read a file = :r stuff.txt
• Scroll Down Half a Window = Ctrl-D
• Scroll Up Half a Window = Ctrl-U
• Execute command = :! Ls
• Get Version of VI = :ver
• Word Count = :%s///gn

Shell

• Enter Shell = :sh

Settings:

• Show Line Numbers = :set number
• No Line Numbers = :set nonumber
• Show Status Line = :set laststatus=2
• Stop Status Line = :set laststatus=0
• Show Special Characters = :set list
• Stop Special Characters = :set nolist

Windowing:

• Split Window = :sp
  • Move up a window = Ctrl-W j
  • Move down a window = Ctrl-W k
• Highlight Search Option: :set hlsearch
• Incremental Searches: :set incsearch
• Redraw Screen = Ctrl-L

Search / Replace:

• Delete all ^M = :%s/Ctrl-VCtrl-M//g
• CaSE Sensitivity: /\Csmith will find "Smith", "Smithsonian", etc.
• CaSE InSensitivity: /\cjohn will find "john", "John", "JOHN", "Johnson”, "johnSON", etc.

Cursor Position:

• Store current position in the 't' mark = mt
• Go to the line stored in the 't' mark : 't
• Note: 't' can be any character, think of it as a location buffer. Ex ma, then 'a

Other:

• You Mistakenly Edit a ReadOnly File but need to save it now: :w !sudo tee % >/dev/null
• ~/.vimrc comment line, use 1 double-quote followed by comment text = " Comment text
• Change background color to black if it's grey, while inside vi: :colo torte
• Turn syntax highlighting on, while inside vi: :syn on

VMSTAT (Reports Virtual Memory Stats)

Display a Quick Summary: vmstat –s

Display in 1 second intervals, 5 times: vmstat 1 5

VNC Server

On the Linux Server:

• Configure Firewall
• Open Port: 59xx, where xx = the display number. Default Port is 5901

To start KDE or Gnome in VNC:

• Edit /root/.vnc/xstartup
• Uncomment 2 top lines
• Add at end: "startx &" for gnome or "startkde &" for KDE
• vncserver
• set password
• if you need to change it use: vncpasswd
• if you want to delete it: rm /root/.vnc/passwd
• Note the Display number (:1)

On VNC Client:

• <vncserverIP:display number>
  • Ex: Myserver:1
• To Kill a VNC desktop that was started with vncserver (this kills the Xvnc process)
  • vncserver –kill:display#
  • Ex: vncserver –kill :1

Install VNC Server on Ubuntu MATE using Desktop Display:

• 1. Install Ubuntu Mate 18.04 LTS
• 2. Install VNC Server: sudo apt-get install vnc4server
• 3. Start the Server: vncserver :1
• 4. Kill the Server: vncserver -kill :1
• 5. Edit the generated configuration file:
•   5.1 sudo vi ~/.vnc/xstartup, add these 2 lines at the bottom of the file:
•     5.2 unset DBUS_SESSION_BUS_ADDRESS
•     5.3 mate-session
• 6. Start the server: x0vncserver -passwordfile ~/.vnc/passwd -display :0 # This starts a server on the default port of 5900 and attaches to the current display
•   6.1 To start the server in the background: x0vncserver -passwordfile ~/.vnc/passwd -display :0 >/dev/null 2>&1 &
• 7. Check if your server is running: fuser -vn tcp 5900
• 8. Connect from Windows or other OS by using: VNC Viewer (RealVNC)
• 9. To stop the server, find the x0vncserve process ID, then kill -9 <pid>


• Note: x0vncserver will use the screen geometry of the actual display.
• Note: x0vncserver is supplied w/ vnc4server package

VSFTP

By default, vsftpd displays directory listings in GMT, to set this to list files in your local time, use:

• echo "use_localtime=YES" >> /etc/vsftpd/vsftpd.conf
• service vsftpd restart

Wall (Send a Message to Everybody’s Terminal)

To send a broadcast message to everyone’s terminal: wall –n message ctrl-D

Without –n the banner reads: ex.: "Broadcast message from root (pts/2) (Sat Jul 15 10:11:58 2006):"

With –n the banner reads : "Remote broadcast message (Sat Jul 15 10:12:51 2006):"

Watch

Executes a program periodically, showing output fullscreen

To watch the contents of a directory change every 15 seconds:

• watch –n 60 –d ls –l

Who is logged in and What they are doing

w

Wireless configuration

iwconfig

Wireless Monitoring:

• Show the Link Quality, Signal Level and Noise Level: iwconfig wlan0
• Show the same info as above, in different format: cat /proc/net/wireless
• Continuously monitor the Wireless Connection: watch -n 1 cat /proc/net/wireless
• To see the associated SSID: iwgetid
• To see more detailed wireless information: iwlist

Write (Send a Message to another user)

Usage: write user [ttyname]: write root pts/2 message

Your Identity, Your Group, etc.

id

Yum

Exclude Package(s) from Updating: yum update –exclude=389-*

List Installed Packages: yum list installed

Install packages automatically without asking any confirmation: yum –y install updates

Remove a Package: yum remove package_name

Update a Package: yum update package_name

Search for a Specific Package in the Repository: yum list package_name

Search for a Package, w/o knowing Exact Name: yum search package

List Information about a Package: yum info package

Find which Package a Specific File belongs to: Ex. yum provides /etc/httpd/coonf/httpd.conf

List Enabled Package Repositories in your System: yum repolist

List all Enabled and Disabled Repositories in your System: yum repolist all

Install a Package from a Specific Repository: Ex. yum –-enablerepo=epel install phpmyadmin

Temporarily allow a repo and install php from it: Ex.yum –-enablerepo=remi install php

Temporarily disable a repo: Ex. yum –-disablerepo=epel-testing

Permanently enable a repo. Here’s a remi example::

• vi /etc/yum.repos.d/remi.repo
• Change enabled=0 to enabled=1

Clean the Yum Cache: yum clean all

View Yum History – List all Yum Operations

• yum history (works w/ RHEL 6+)
• or cat /var/log/yum.log (RHEL 5+, 6+)

View Update History Information by ID: yum history info <ID>

Undo / Rollback a Transaction ID: yum history undo <ID>

VMWare: Extending a logical volume in a virtual machine running Red Hat or Cent OS

LVM – Expanding the Disk Size in Vmware:

1. Expand the drive size (Disk Capacity) in VMWare
2. Boot the OS, ID the device name and confirm the new disk size: fdisk –l (/dev/sda by default will be expanded)
3. Create a new Primary Partition: fdisk /dev/sda
   1. p (you’ll see all the existing partitions, not the new space yet)
   2. n (create a new primary ookingn)
   3. p (it will auto-select the partition for you, ex. 4)
   4. Enter (default 1st cylinder)
   5. Enter (default last cylinder)
   6. p (now you’ll see the new space as the new partition, ex. /dev/sda4)
   7. t to change system’s partition ID to LVM
   8. <new_partition_number>, ex. 4
   9. 8e to change the Hex Code of the partition to Linux LVM
   10. w to Wrtie change to the partition table
4. Reatart the VM
5. fdisk –l (check to see the new partition, ex. /dev/sda4 is LVM w/ Id 8e)
6. Convert the new partition to a physical volume: pvcreate /dev/sda4
7. Extend the volume with the new partition / Physical volume: vgextend VolGroup00 /dev/sda4
8. Confirm: vgdisplay – look for VG Size
9. Verify how many physical extents are available to the VG by ooking at the "Free PE / Size" line of the vgdisplay command
10. Extend the Logical Volume in order to use the new underlying storage we expanded: lvextend –L+<#G> /dev/VolGroup00/LogVol00 – where #G is size found in Step 9. OR extend by the amount of free space on the volume: lvextend /dev/VolGroup00/LogVol00 /dev/sda4
11. Expand the ext3 filesystem online, inside the Logical Volume: resize2fs /dev/VolGroup00/LogVol00
12. Verify extra space: df –h /

zip

Test the integrity of a zip file (verify contents): unzip -t <filename>.zip

More Unix Commands

UNIX COMMANDS continued…