Hey Folks, ✌️
Welcome to another one! 😊
Here , we will deep dive into commands is used by DevOps engineers for day-to-day activities. Command are most important on when comes to Linux. Its Cloud or On-premises at the end we mostly use Linux based machines. We must know about the commands to run the tasks efficiently.
File System:
df -hT --> Check the files system, partiton status
fdisk -l --> Check the device all disk details
tree -a --> Check direcotory structure
du -sh * | sort -h | tail -n 20 --> Sort the file the Size in current directory
du -a /dir/ | sort -n -r | head -n 20 --> Sort the file the Size inlude directory
cat /etc/fstab --> Check the current disk mounts,Partition
mkdir -p /tmp/sub_folder1/sub_folder2 --> Create sub directories
Process:
ps -aux | grep -i nginx --> Check the nginx process,PID,user,etc
ss -tunlp | grep -i nginx --> Check the nginx servie is listening
journalctl -f -u nginx --> Check the service logs for nginx
lsof /dev/null --> Check Open Files
lsof -u karthick --> Check Open Files for user karthick
lsof -i TCP:80 --> Check Open Files for port 80 used
top --> Task Manager ( Process,CPU,Memory )
htop --> Advanced Task Manager
free -h --> Check RAM info
lscpu --> check the CPU info
sync; echo > 3 /proc/sys/vm/drop_caches --> Remove the cache memory
pkill <process> --> Kill the process
kill -9 <PID> --> Kill the pid of the process
loginctl --> Login session details
logintctl terminate-user <user_name> --> Terminate the user who logged
Service:
systemctl status nginx --> Check 'nginx' status
service nginx status --> Check 'nginx' status
sudo systemctl restart nginx --> Restart 'nginx' status
ss -tunlp | grep -i nginx --> Check 'nginx' port
Package:
apt install <package> --> Install the package
apt remvoe <package> --> Remove the package
apt purge <package> --> Remove the package also data,config files
apt autoremove --> Remove unused packages
apt update --> Update the application packages
apt upgrade --> Upgrade the all packages
dpkg -i <package.deb> --> Install the downloaded package.deb file
Misc:
sudo echo "shutdown -h now" | at -m 00:00 --> Shutdown the machine at 12 AM ( without using Crontab )
atq --> List jobs in at
atrm 2 --> Delete the 2nd task
init 6 --> Restart the machine
Text Search:
Advanced :
&& --> Execute when first command sucess, then proceed next command
Ex: apt update && upgrade
|| --> Execute when first command failed, then proceed next command
Ex: apt update || apt autoremove
; --> Execute the command continuosly
Ex: echo 1; echo 3;
Text:
grep karthick log.txt --> search "karthick" in file
grep -i karthick log.txt --> search ( Karhick,KARTHICK) without case-sensitive
grep "text1|value1" log.txt --> use two values in log
awk '{print $2}' /file --> Print 2nd column files in all lines
awk 'NR==1 {print $2}' file --> Print '1st' row and '2nd' Column only
grep -rin "host_name" --> search 'host_name' for all files in current directory
diff log1.txt old_log.txt --> Check diffrence of two files
VIM:
# Command Mode ( Press " : " for goto command mode )
:$1,%s/abc/xyz/g --> Replace "abc" vaules into "xyz"
/abc --> search "abc" in file
:x --> Save and Quit
:se nu --> Set line numbers
# Normal Mode:
yy --> Copy the full line
p --> Paste the copied line
dd --> Delete the line
# Insert Mode
i - Go to insert mode
R - Replace
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Medium: karthidkk123.medium.com
Github: github.com/karthick-dkk