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  • What is the difference between "su" and "su -" ?


    If we check the man page for su
    su - run a shell with substitute user and group IDs

    which means that if you use
    # su -
    you are switching user to the root user and asking the system to change all the environment variables applicable to root and take me to the root's home directory

    Using su - is same as logging into a fresh session on a terminal

    For example
    [deepak@server ~]$ pwd
    /home/deepak

    [deepak@server ~]$ echo $PATH
    /usr/bin:/usr/sbin:/usr/local/bin:/bin:/usr/bin:/home/deepak/bin

    [deepak@server ~]$ sudo su -
    [root@server ~]# pwd
    /root

    [root@server deepak]# echo $PATH
    /usr/bin:/usr/sbin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

    But when you type only su without a dash(-) in that case the session is switched to root(if any username is not mentioned along with su command) without applying any of the environment variable of the root user.





    Also the new user stays in the same directory as he was before using su
    [deepak@server ~]$ echo $PATH
    /usr/bin:/usr/sbin:/usr/local/bin:/bin:/usr/bin:/home/deepak/bin

    [deepak@server ~]$ pwd
    /home/deepak

    [deepak@server ~]$ sudo su
    [root@server deepak]# pwd
    /home/deepak

    [root@server deepak]# echo $PATH
    /usr/bin:/usr/sbin:/usr/local/bin:/bin:/usr/bin:/home/deepak/bin


    I hope the article was useful.

    Deepak Prasad

    is a techie and an author who is still trying to survive in this IT generation with very little knowledge he has on Linux/Unix, VMware, SAN Storage, Automation, networking etc

    You can follow him on Facebook or Google+

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    What is the difference between "su" and "su -" ? What is the difference between "su" and "su -" ? Reviewed by Deepak Prasad on Thursday, January 30, 2014 Rating: 5

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