CentOS Cheat Sheet

A Software › Linux cheat sheet in English by mrinflictor

Performing basic tasks in CentOS

30,761 views 9,742 downloads 14 Jul 2014 History

PRs

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I/O Redirection

>	Redirect STDOUT to a file
2>	Redirect STERR to a file
&>	Redirect all output to a file
2>&1	Redirect all output to a pipe
cmd1 \| cmd2	Pipe STDOUT of cmd1 to cmd2

Use >> to append rather than overwrite

Scheduling with cron

#list current entries in crontab
crontab -l
#remove current entries in crontab
crontab -r
#edit existing entries in crontab
crontab -e
#format
<minute> <hour> <day of month> <month> <day of week> <command>

File Management

find / -name tofind	Find all files named tofind
find / -mmin 10	Find all files modified less than 10 minutes ago
grep -i STRING	Search input for lines containing STRING (nocase)
grep -C 2 STRING	Search input for lines containing STRING and showing 2 lines before and after
grep -v STRING	Search input for lines NOT containing STRING
grep -c STRING	Search input for number of lines containing STRING

Bash Shortcuts

CTRL-c	Kill current command
CTRL-a	Goto start of current line
CTRL-e	Goto end of current line
CTRL-r	Search history
!!	Repeat last command
^abc^def	Run previous command, replacing abc with def

Useful Snippets

#hostname

Displays FQDN of system

#uname -a

Displays current kernel version

#df -h

Display partitions, sizes details, and mount points

#chconfig --list

Displays all services and their status at each runlevel

File Paths

/var/named

Bind zone files

/etc/named.conf

Bind configuration file

/etc/httpd/conf/httpd.conf

Main apache configuration file

/var/log/httpd/

Default location for logs

/etc/hosts

System hosts file

/etc/resolv.conf

DNS lookup configuration file

/etc/sysconfig/network

Network/hostname configuration file

/etc/sysconfig/network-scripts/

Default location of a network setting file

Archiving

# compress (tar/gzip)
tar cvzf <file>.tgz <directory>
# extract (tar/gzip)
tar xvzf <file>.tgz
# compress (tar/bzip)
tar cvjf <file>.tbz <directory>
# extract (tar/bzip)
tar xvjf <file>.tbz
# extract (gzip)
gunzip <file>.gzip

Screen shortcuts

CTRL-a c	Create a new screen session
CTRL-a n	Goto the next screen session
CTRL-a p	Goto the previous screen session
CTRL-a "	Present a list of all sessions
CTRL-a d	Detach screen from terminal
CTRL-a k	Kill current session

screen -r to reattach to a detached session

iptables

#iptables -L

Displays ruleset of iptables

#iptables -I INPUT -p tcp -m tcp -s 192.168.15.254/26 --dport 22 -j ACCEPT

Accepts incoming SSH connections from IP range 192.168.15.254/26

#iptables -I INPUT -s "192.168.10.0/24" -j DROP

Drops all traffic from IP range 192.168.10.0/24

#iptables -A INPUT -p tcp --dport 25 -j DROP

Blocks all traffic to TCP port 25

#/etc/init.d/iptables save

Saves all IPtables rules and re-applies them after a reboot

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Comments (2)

kashbrook 23:32 16 Jul 2018

Thanks for making this cheat sheet.

Andreas Hinderberger 15:30 14 Dec 2014

Hi, thanks for the nice sheet, but you have a typo in there: #chconfig --list should be #chkconfig --list