Questions[su](server)

I am working on automating the creation of subversion repositories and associated websites as described in this blog post I wrote. I am running into issues right around the part where I su to the www-data user to run the following command:

svnadmin create /svn/repository

There is a check at the beginning of the script that makes sure it is running as root or sudo, and everything after that one command needs to be run as root. Is there a good way to run that one command as www-data and then switch back to root to finish up?

All I need to do is to run a specific script as a particular user who does have the nologin/false shell indicated in /etc/passwd.

I would run the script as root and this should run as another user. Running:

~# su -c "/bin/touch /tmp/test" testuser

would work, but I need a valid shell for the testuser. I know I can disable the password with passwd -d testuser and leave the shell to /bin/bash this way would secure a little bit but I need to have nologin/false shell.

Basically what I need is what crontab does when we set jobs to be running as a particular user, regardless this one has nologin/false shell.

p.s I found this thread Executing a command as a nologin user, but I have no idea how to concatenate the command su -s /bin/sh $user to the script I need to run.

I've recently set up my server so that my suPHP 'virtual' users can't be logged into by using this article

My issue now is that before when I ran a rake command for my Ruby on Rails application running on the server, I used su to go into www-data and execute the command from there - obviously I can't do that anymore because of the nologin.

So as a root user, how can I execute commands as other user's, even if they are nologin?

I was su'ed into a user to run a particular long running script. I wanted to use screen but I got the error message "Cannot open your terminal '/dev/pts/4' - please check."

So I Googled around and came across a forum post that instructed to run $ script '/dev/null/'. I did so and then I could screen.

Why does this work? What is su doing that screen cannot run as the su'ed user? Why does re-directing 'script' to /dev/null do that is prevented otherwise? Is it using script to write a log as the original user to somewhere?

How do you allow a user to log in using "su - user" but prevent the user from login in using SSH?

I tried to set the shell to /bin/false but the when I try to su it doesn't work.

Are there several ways to only allow logins by su?

Is SSH's AllowUser the way to go? (how would I do this if it's the way to go)