Linux Basics

These commands are from RedHat. So, it might change based on Unix Flavor.

  • To check the Unix Flavor running on the machine use “uname -a” or “cat /proc/version
  • To check how many users are configured in local machine
    • Check the name list in /home directory. Use “ll” or “ls –l”
    • Check the /etc/passwd file. “cat /etc/passwd”
      • Each entry in the /passwd file would be “login-name:password (shown as ‘x’ in to hide/shadow):user ID:group ID:user detail:home directory:shell
  • Actual password would be in “/etc/shadow” file in encrypted form. Only root can access.
  • The groups which a user belongs to will be in “/etc/groups” file.
  • We can see the available shell prompts in “cat /etc/shells” command
  • Users can be added via “useradd <name>” and “passwd <name>” command.
  • “chmod” to modify the mode of a file.
    • First letter will say whether it is directory or single file. d or –
    • First ‘rwx’ shows the read,write,execute permission for the user who created that file.
    • Second ‘rwx’ shows the above permission for users of same group
    • Third ‘rwx’ shows the permission for all other users.
    • “Chmod 750 file-name” will make the mode of that file as 111-101-000
  • We can install application using “apt-get” or “yum” command. [Provided yum is installed]

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