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Disk:
  • Find a file (recursive): find / -iname '*.sql'
  • Copy with modification time: rsync -t sourceFile.txt destPath
  • Copy with modification time and owner/group: rsync -a sourceFile.txt destPath
  • Make a backup of files in folder: rsync -arv inwar/ inwar-bak/
  • Convert zip to gzip: unzip -p file.zip | gzip > file.gz
  • gzip and keep original file: gzip -c hugeFile.txt > hugeFile.txt.gz
  • gzip a folder: tar -czvf folder.tar.gz /path/to/dir
  • Extract a gzipped folder: tar -xzvf folder.tar.gz
  • What process has a folder/file open: lsof +D <path>
  • Disk space free on drive: df -h
  • Disk space of a folder: du -sh
  • Disk space of subfolders: du --max-depth 1 | sort -n
  • RAM and swap usage: free -mt
  • Disk bandwidth usage: iotop
  • Replace text in all files in a folder (recursive): find ./ -type f -exec sed -i 's/apple/orange/g' {} \;
Linux Users:
  • Create user: useradd -m -s "/bin/bash" <username>
  • Set password: passwd <username>
  • Remove user: userdel -r <username>
  • Create group: groupadd <groupname>
  • Create user and add user to group: useradd -G <groupname> <username>
  • Add user to group: usermod -a -G ftp tony
  • Add user to sudoers:

    • on Ubuntu: usermod -a -G sudo <username>

    • on CentOS:

       groupadd sudo
 visudo and add: %sudo ALL=(ALL) ALL
 usermod -a -G sudo <username>
To install Nano:
  • yum install sudo nano
  • in ~/.bashrc : export EDITOR=nano
Misc Commands:
  • Find what packages use a package: aptitude why <package>
  • Shutdown server: shutdown -h 0
  • Find OS version: cat /etc/issue
  • Remotely share bash: tmux
  • Find in man: /term
  • Copy stdout to clipboard over ssh: | xclip -i
  • Look at auto start services: chkconfig
  • Restart a service: service <name> restart
  • Kill a process: kill -9 <pid> or pkill -f <proc_name>
  • Run the last command with sudo: sudo !!
top:

top - to display info about processes
? - to get help when top is running

  • Linux (CentOS):

    < - move sort field left
    > - move sort field right
    O - to select the sort field
    n - to sort by memory usage
    k - to sort by CPU usage

  • OS X:

     top -o cpu
 top -o mem
🔑 SSH

  • To set up SSH public-key authentication to connect to a remote server:

     scp ~/.ssh/id_rsa.pub username@server:
 ssh username@server
 cat id_rsa.pub >> ~/.ssh/authorized_keys
 cat ~/.ssh/authorized_keys
 rm id_rsa.pub
 exit
 ssh username@server
🔑 ROT13 cipher

  • with tr translate characters command:

     # Map upper case A-Z to N-ZA-M and lower case a-z to n-za-m
 echo "The Quick Brown Fox Jumps Over The Lazy Dog" | tr 'A-Za-z' 'N-ZA-Mn-za-m'