Linux Shell Skills

Categories

Introduction

Shell Scripting

Rename suffix of mulitple files

# https://unix.stackexchange.com/questions/19654/how-do-i-change-the-extension-of-multiple-files
# Rename all *.txt to *.text
for f in *.txt; do
    mv -- "$f" "${f%.txt}.text"
done

SSH

Include SSH config from multiple files

  • Create SSH config folder, then add an example config
mkdir ~/.ssh/config.d/
touch ~/.ssh/config.d/example
  • Edit ~/.ssh/config
Host *
    ForwardAgent yes
    ServerAliveInterval 120
    ServerAliveCountMax 2
    GSSAPIAuthentication no

Include config.d/*

Host production-1
	HostName 127.0.0.1
	User root
    Port 22
  • Edit ~/.ssh/config.d/example, add example config content 
    Host production-2
  HostName 127.0.0.1
  User root
  Port 22

Get Public SSH Key from Private SSH Key

ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub
ssh-keygen -l -f ~/.ssh/id_rsa

# https://blog.tinned-software.net/generate-public-ssh-key-from-private-ssh-key/

Change hostname

hostnamectl set-hostname name

OpenSSL

https://support.f5.com/csp/article/K11440

Ubuntu

https://linuxize.com/post/how-to-set-or-change-timezone-on-ubuntu-18-04/

Cronjob

# Restart machine every day
0 2 * * * root /sbin/shutdown -r +5

https://tecadmin.net/crontab-in-linux-with-20-examples-of-cron-schedule/

SELinux

https://linuxhint.com/how-to-disable-selinux-on-centos-7/

Find My Public IP from Command Line

dig +short myip.opendns.com @resolver1.opendns.com

curl ifconfig.co
curl ifconfig.me

https://www.cyberciti.biz/faq/how-to-find-my-public-ip-address-from-command-line-on-a-linux/

Is there a way for one SSH config file to include another one?

tcpdump

https://hackertarget.com/tcpdump-examples/

journalctl

https://unix.stackexchange.com/questions/225401/how-to-see-full-log-from-systemctl-status-service

Yum

How to restrict yum to install or upgrade a package to a fixed specific package version?

Clear Cache

How to Clear RAM Memory Cache, Buffer and Swap Space on Linux