set-uid bit: where am I going wrong?

[Lowell Gilbert]

Tim Stephens <tim at tjstephens.com> writes:

> I'm trying to use a script I wrote to copy files from one directory to another (as part of my backup regime). Unfortunately,  because they are in my webserver directory, some of the files don't belong to the user that I run the script as (via cron). I can run the script with sudo, so I know that it's a permission problem. 
> 
> My initial thought is that I can use the set-uid bit and chown the script to root, but this still balks. Here is the relevant output of ls -l.
>  
> -rwsr-xr-x   1 root  admin   283 Nov 23 15:58 buprep.yuri
> 
> Clearly the file is owned by root, and I kept it as part of my group. I've read the man pages, and believe that when I call the script, it will assume root's permissions. It doesn't, so where am I going wrong?

The kernel ignores the setuid bit on interpreted files, for security
reasons.