Linux System Administration

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Managing User Accounts

Switching User and Switching Group

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Commands for Switching Users and Groups in Unix-like Systems

CommandPurposeKey OptionsExample
suSwitch user or execute commands as another user- (start login shell), -c command (run command as another user)Example:
1. Switch to user john: su - john
2. Run a command as john: su -c "ls /home/john" john
sudoExecute commands as another user or root-u user (run as another user), -i (run as login shell)Example:
1. Run a command as john: sudo -u john ls /home/john
2. Start a new login shell as john: sudo -u john -i
newgrpChange the current group ID during a sessionNoneExample:
1. Switch to the developers group: newgrp developers
sgRun a command with a different group IDgroup (group name)Example:
1. Run ls with developers group ID: sg developers -c "ls /home"

Example Usage:

  1. Switch User with su:
    • Switch to user john:bashCopy codesu - john This switches to user john and starts a new login shell. You will be prompted for john‘s password.
    • Run a command as john:bashCopy codesu -c "ls /home/john" john This runs the ls /home/john command as user john without switching to their shell.
  2. Execute Commands as Another User with sudo:
    • Run a command as john:bashCopy codesudo -u john ls /home/john This runs ls /home/john as user john, using sudo for privilege escalation.
    • Start a new login shell as john:bashCopy codesudo -u john -i This starts a new interactive shell as user john, similar to su - john.
  3. Change Group ID with newgrp:
    • Switch to the developers group:bashCopy codenewgrp developers This changes the current group ID to developers within the current shell session, affecting file creation and permissions.
  4. Run Commands with a Different Group ID using sg:
    • Run ls with the developers group ID:bashCopy codesg developers -c "ls /home" This runs the ls /home command with the developers group ID.