hi guys,

just reading in the Dutchmans Red Hat manual,

it says:

When using su , a sub shell is started. This is an environment where you are able to work as the target user account, but environment settings for that user account have not been set. If you need complete access to the entire environment of the target user account, you can use su - to start a login shell. If you start a login shell, all scripts that make up the user environment are processed, which makes you work in an environment that is exactly the same as when logging in as that user.

thats all fine,and i understand it...

but when would you want to login with the complete user environment,and when wouldnt you?

is it more to do with bash scripting and testing things?

Hum...
I always kinda, sorta assumed the su - form was expressly to let you use your accounts locally defined environment variables. Back in the days of HP and Sun workstations, that seemed like reason enuf.

Was I wrong in thinking that?

Use "su" when you're currently doing something that temporarily needs root permission, eg: you just ran make and now need to run make install. "su" will leave your environment and working directory alone so you can simply run "make install" after the su, without having to cd all over the place and possibly copy/paste any necessary environment variable declarations for the build to work correctly.

Use "su -" when you need to do a task as root that has nothing to do with what you've been doing previously in the terminal, in which having a clean shell with root's proper PATH and other environment variables would be beneficial (eg: /sbin and /usr/sbin are usually not in regular users' PATH, so you want to use "su -" to load up root's full environment to have access to those programs).

1 members found this post helpful.

"su -" is just the short form of this command
su you become root BUT!!!! with your users $PATH and system settings
as above any program in /sbin you need to be fully logged in as root

Actually, su <anyuser> logs you in as anyuser, but with your env not theirs. No user specified defaults to root.

"su - <user>" logs you in as anyuser with THEIR env. No user specified defaults to root (with root's env).