su vs. 'su -' The Mystery Revealed2008-06-24
Inquiring minds want to know, what is this su - and why is it different than su? Well, if you are like me, you didn’t even know that su - existed. I ran into this problem when I was trying to add a new user to a new Linux machine. Remote root login was disabled(for obvious reasons:D) and I was logged in with my regular non-privileged user account. Well, normally the story goes like this...
- useradd account
- set password
- log out of privileged account
- Take coffee break from all the hard work and call it a day
No so today:( . When I attempted to run step three(useradd), I received a command not found error. "That's weird" I thought. How could a machine not have this basic command. I looked in the bin directory to see if it was some kind of path error I was having. Thinking that this was the case, I was shocked to see that none of the user commands(adduser, usermod, deluser) where there.
After a few minutes of scratching my head, I asked someone more versed in Linux than I what they thought. After walking through each of the steps I had taken, my mistake was easily spotted. I hadn’t added the - to the su command. Thinking that the explanation was weird, I checked with google for the su - command. Sure enough, the link to Wikipedia had this to say about it,
Optionally, you can use a hyphen with su to invoke a login shell and assume the target user’s complete user environment:
I am glad I had someone to point this out to me… It could have been a longer and very frustrating ordeal. It was also a lesson for me to refer more to the man pages(it had the answer there too). I hope this blog entry helps someone else who is confronted with this situation.