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Linux commands Cheat Sheet (DRAFT) by

Linux commands for DevOps

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Basic info

pwd
show present working directory
uname
show name of the kernel
uname -r
show kernel version
cd
change directory
clear
clear the screen
whoami
show current login user name
history
show list of previously used commands
date
show time and date
echo "­Hel­lo"
display Hello text
sudo
run commands as super user

Working with directory and files

mkdir dir
create single directory dir
mkdir dir1 dir2
create multiple direct­ories dir1 dir2
mkdir -p dir/a/b/c
create nested directory dir/a/b/c
mkdir dir{1..10}
created 10 numbered direct­ories from dir1 to dir10
rm -r dir
remove dir recurs­ively
touch file
create empty file file
touch file1 file2
create multiple files file1 file2
touch file{1..10}
create 10 numbered files from file1 to file10
cp -rf /dir/file1 /dir2
copy file file1 to dir2 directory recurs­ively and forcefully
mv /dir/file1 /dir2
move file file1 to dir2 directory
rm file1
remove file file1
ls -al
show files - both regular & hidden files and their permis­sions
cat file1
display contents of file1
find /dir1 -name file1
find file1 under /dir1 directory
find /dir1 -perm 664
find all files/­dir­ect­ories with read, write permission to owner and group, read permission for others in directory dir1
find /dir1 -empty -exec rm -r {}**
find and remove all empty files/­dir­ect­ories from /dir1
wc -l file1
count the number of lines in file1
wc -w file1
count the number of words in "­file1*
head file1
display top 10 lines of file1
head -n 20 file1
display top 20 lines of file1
tail file1
display last 10 lines of file1
tail -n 20 file1
display last 20 lines of file1

Networking

ifconfig or ip addr
show ip address
nmcli con show
show list of connec­tions
nslookup
queries the DNS server for inform­ation about a domain name or IP address
iptables
sets up, maintains, and inspects the tables of IPv4/IPv6 packet filter rules in the Linux kernel firewall
ping host
send packets to host to check the connec­tivity
ping -c 5 host
send 5 packets to host
curl
facili­tates the transfer of data to or from a server, using any of the protocols it supports
netstat
Displays network connec­tions and network statis­tics, such as active sockets, routing tables, and network interface statistics
ss-keygen
Creates a pair of public and private authen­tic­ation keys
ssh user@host
connect user to host using ssh
scp file1 user1@­hos­t:/dir
copy file1 from local to remote host host to /dir location

System and process monitoring

uptime
show current uptime
df
show disk usage
du
show directory space usage
free
show memory and swap usage
ps
show all current active processes
top
task manager program displays inform­ation about CPU and memory utiliz­ation
kill pid
kill process with process id pid
bg
list stopped or background jobs
lsof
Lists all files opened by any process of a system
lsof -u user1
Lists all files opened by user1
 

File permis­sions

chmod [symbolic] file1
change file permis­sions of file file1 based on [symbolic] code
chmod u+r file1
add read permission to owner for file1
chmod g+rw file1
add read, write permission to group for file1
chmod o-r file1
remove read permission to others for file1
chmod [octal] file1
change file permis­sions of file file1 based on [octal] code
chmod 777 file1
add read, write, execute permission to owner, group, others for file1
chmod 754 file1
add read, write, execute persmi­ssion to owner, read and execute permission to group, read permission to others for file1
chown user1 file1
change ownership of file1 to user1
chgrp group1 file1
change group ownership of file1 to group1
setfacl -m u:user­1:rwx file1
add read, write, execute permission to user user1 for file1
setfacl -x u:user1: file1
remove all permis­sions for user1 for file1
setfacl -b file1
remove all acl permis­sions for file1

User and Group Management

useradd user1
create user1 user account
passwd user1
create password for user1 user
su
switch user account
exit
logout user
userdel user1
delete user account user1
usermod -l user2 user1
change user1 login name to user2
groupadd group1
add group group1
groupdel group1
delete group group1
gpasswd -a user1 group1
add single user user1 to group group1
gpasswd -M user1,­user2 group1
add multiple users user1 user2 to group group1
gpasswd -d user1 group1
remove user user1 from group group1
gpasswd -A user1 group1
make user1 as admin of group1

Text search and manipu­lation

grep text file1
display the lines that contains text in file1
grep -ni text file1
ignore the case and display line numbers of the matched lines
awk -F',' '{print $1"@­­"$3}'
print col1@col3
awk -F'\t' '/str/ {print $0}'
print line with str

Compress and archive

tar -cf /dir1/­bac­kup.tar /dir2
create tar archive file /dir1/­bac­kup.tar for /dir2
tar -xvf /dir1/­bac­kup.tar -C /dir2/
extract tar archive file /dir1/­bac­kup.tar to /dir2/

cron jobs

at time
schedule command to run at time
atq
view pending jobs
atrm 2
remove job 2 from the scheduled commands
crontab -e
set cron jobs
0 2 * * * /dir1/­scr­ipt.sh
run script /dir1/­scr­ipt.sh at 2pm daily
crontab -l
show the list the cron jobs of current user

Package management

apt update
update the local package index with the latest changes made in the reposi­tories
apt upgrade
upgrade installed packages
apt install package
install package
apt remove package
remove installed package
systemctl start service
start service
systemctl status service
check the status of service
systemctl stop service
stop service
systemctl enable service
enable the service to start at system startup