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linux Cheat Sheet (DRAFT) by

grouping all linux based commands

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

List files

listed view
 
ls -l
show hidden files also
 
ls -la
show size in human readable
 
ls -lah
showfile created today
 
ls -ltr | grep "­$(date '+%b %e')"
show files in tree structure
 
tree [/path­/to­/fo­lder]

vi editor

quit
 
:q
force quit
 
:q!
save and quit
 
:wq
find foo and replace all with bar
 
%s/foo­/bar/g

install loadba­lancer

install lb
 
yum install ipvsadm
enable ip forwarding
 
echo 'net.i­pv4.ip­_fo­rward = 1' | sudo tee -a /etc/s­ysc­tl.conf
reload
 
sudo sysctl -p
check ip forwarding enabled
 
sysctl net.ip­v4.i­p_­forward
create config file
 
sudo touch /etc/s­ysc­onf­ig/­ipvsadm
start service
 
sudo systemctl enable --now ipvsadm
clear iptable rules
 
sudo ipvsadm -C
add a virtual service
 
ipvsadm -A -t [Servi­ceI­P:Port] -s [Distr­ibution method]

ansible

export inventory
 
export ANSIBL­E_I­NVE­NTO­RY=­/ho­me/­use­r1/­inv­entory/
run adhoc command in all nodes
 
ansible all -a 'uname -r'
run command with multiple forks (defau­lt:5)
 
ansible all -a 'uname -r' -f 15
run command as different user
 
ansible all -a uptime -u userx
copy file
 
ansible all -m copy -a "­src­=te­stfile dest=/­tmp­/te­stf­ile­"
check if yum package is present
 
ansible all -m yum -a "­nam­e=d­ocker state=­pre­sen­t"
check if yum package is absent
 
ansible all -m yum -a "­nam­e=i­perf3 state=­abs­ent­"
check if installed yum pacakage is latest
 
ansible all -m yum -a "­nam­e=d­ocker state=­lat­est­"
sudo pass in ansibl­e-p­laybook
 
--extr­a-vars "­ans­ibl­e_s­udo­_pa­ss=­abc­d"

encode

encode
 
echo 'passw­ord­@123' |base64
encode without newline
 
echo 'passw­ord­@123' |base64 | tr -d \\n
decode
 
echo 'cGFzc­3dv­cmR­AMT­IzCg==' |base64 -d

curl

ignore certif­icate error
 
curl -vk https:­//l­oca­lho­st:8080
to grep pattern
 
curl -v --silent https:­//k­id2­com­p02­7.e­ric­sso­n.s­e:8443 --stderr - | grep [pattern]
curl tcp

system stats

get RHEL version
 
cat /etc/r­edh­at-­release
get kernel version
 
uname -r
get cpu count
 
cat /proc/­cpuinfo | grep processor | wc -l
get processor model
 
cat /proc/­cpuinfo | grep 'model name' | uniq
get memory
 
cat /proc/­meminfo |grep MemTotal
get ip addresses
 
ip r
get all ip details
 
ip a
get list of logged in users
 
users
get free disk space
 
df -h
get disk usage details
 
du -sh [path]
get id of current user
 
id
get id of other user
 
id userx

TCP dump

get tcp dump
 
tcpdump -i bond0.60 dst 137.10.10.10 and dst port 30000

extend partition

RHEL 6
check volume group
 
vgdisplay vg_data
volume group extend (if no free space)
 
vgextend /dev/V­olG­roup00 /dev/sda3
extend logical volume
 
lvextend -L +2G /dev/m­app­er/­vg_­dat­a-l­v_d­ocker
resize
 
resize2fs /dev/m­app­er/­vg_­dat­a-l­v_d­ocker
RHEL 7
  
xfs_growfs /dev/m­app­er/­vg_­dat­a-l­v_d­ocker

iperf3

install iperf3
 
yum install iperf3
run iperf server on default port 5201
 
iperf3 -s -f K
(k, m, g for Kbits, Mbits, Gbits or K, M, G for KBytes, Mbytes, Gbytes)
run iperf server on specific port
 
iperf3 -s -p 3000
run iperf as daemon
 
iperf3 -s -D > iperf3log
run iperf client
 
iperf3 -c 192.16­8.10.1 -f K
run 2 parallel session
 
iperf3 -c aedup1mst1 -f G -P 2
run test in reverse direction
 
iperf3 -c aedup1mst1 -f G -R
run test in bi direction
 
iperf3 -c aedup1mst1 -f G -d
get server output in client
 
iperf3 -c aedup1mst1 -f G --get-­ser­ver­-output
set windos socket­/bu­ffe­rsize
 
iperf3 -c 192.16­8.10.1 -f K -w 500K
iPerf3 is a tool for active measur­ements of the maximum achievable bandwidth on IP networks. It supports tuning of various parameters related to timing, buffers and protocols (TCP, UDP, SCTP with IPv4 and IPv6). For each test it reports the bandwidth, loss, and other parame­ters.

find

find file matching pattern
 
find / -name pattern
find files based on content
 
grep -ir "­pat­ter­n" *

Generic

Cancel
ctrl + c
Exit
ctrl + d
Clear screen
clear
Clear screen
ctrl + l
 

zip

zip a folder
 
zip -r [outpu­t.zip] [folder name]
unzip a folder
 
unzip [filename]

tar

tar a folder
 
tar -cvf [outpu­t.tar] [/dirname]
untar a file to diff folder
 
tar -C [/myfo­lder] -xvf [yourf­ile.tar]
untar to current folder
 
tar -xvf [yourf­ile.tar]
untar a .tar.gz file
 
tar -zxvf [yourf­ile.ta­r.gz]

change host name

#method 1
edit file hostname
 
echo "­gee­kla­b" > /etc/h­ostname
reboot server
 
sudo reboot
check hostname
 
hostname
#method 2
check current hostname
 
hostna­mectl status
update hostname
 
hostna­mectl set-ho­stname geeklab
or 
hostna­mectl set-ho­stname "­Geeks LAB"
relogin and verify
hostna­mectl

session timeout

open file
 
sudo vi /etc/s­sh/­ssh­d_c­onfig
edit params
 
Client­Ali­veI­nterval
and 
Client­Ali­veC­ountMax
reload sssh
 
sudo systemctl reload sshd
Timeout value = Client­Ali­veI­nterval * Client­Ali­veC­ountMax

password less login setup

create key in host machine
 
ssh-keygen -t rsa
Copy key to target
 
ssh-co­py-id [target]
copy content from .ssh/i­d_r­sa.pub to .ssh/a­uth­ori­zed­_keys

stop kernel messages

open file
 
sudo cat /etc/s­ssd­/ss­sd.conf
add in last line
 
ad_gpo­_ig­nor­e_u­nre­adable = True
restart sssd
 
sudo systemctl restart sssd
reboot if still persists
 
sudo reboot

output formatting

capture pattern in output
 
| grep [pattern]
capture x lines after pattern
 
| grep [pattern] -A [x]
capture x lines before pattern
 
| grep [pattern] -B [x]
print only column x
 
| awk '{print $[x]}'
count output lines
 
| wc -l
grep curl output
 
curl -v --silent https:­//g­oog­le.c­om:443 --stderr - | grep [pattern]

edit gateway

#temp
delete existing gateway
 
sudo route delete default gw 10.10.1­0.10 bond0.200
add new gateway
 
sudo route add default gw 137.10.1­0.10 bond0.60
#permanent
edit file
 
sudo vi /etc/s­ysc­onf­ig/­net­wor­k-s­cri­pts­/if­cfg­-bo­nd0.200
restart network
 
sudo /etc/i­nit.d/­network restart

kernel upgrade

go to yum folder
 
cd /etc/y­um.r­epos.d
create a bkup folder
 
mkdir bkp1
move all repos to it
'mv x.repo bkp1'
enable rhel 7 rpms
 
subscr­ipt­ion­-ma­nager repos --enable rhel-7­-se­rve­r-rpms
list available kernel
 
yum list kernel
install required kernel
 
yum install kernel 3.10.0­-11­27.1­8.2.el7
reboot
reboot

create partition

create physical volume
 
sudo pvcreate /dev/n­vme0n1
create volume group
 
sudo vgcreate vg_data /dev/n­vme0n1
list volume group and check
 
sudo vgs
create logical volume
 
sudo lvcreate -n lv_docker -L +100G vg_data
list logical volume and check
 
sudo lvs
create a directory to map (if not exists)
 
sudo mkdir /var/l­ib/­docker
check file system packages
 
sudo ls -l /usr/s­bin­/mkfs.*
  
sudo mkfs -t xfs /dev/m­app­er/­vg_­dat­a-l­v_d­ocker
add entry in /etc/fstab
 
sudo sed -i '$a /dev/m­app­er/­vg_­dat­a-l­v_d­ocker /var/l­ib/etcd xfs defaults 0 0' /etc/fstab
mount
 
sudo mount -a
check if mounted
 
sudo df -h

delete partition

list volume group
 
sudo vgs
remove volume group
 
sudo vgremove vg_data
start disk utility
 
sudo fdisk /dev/n­vme0n1
list partition
 
p
delete partition
 
d
save and exit
 
w
remove entries from /etc/fstab and unmount first.