Editing Setuid (section)

===SUID===
'''4701''' on an executable file owned by 'root' and the group 'root'

A user named 'thompson' attempts to execute the file. The executable permission for all users is set (the '1') so 'thompson' can execute the file. The file owner is 'root' and the SUID permission is set (the '4') - so the file is executed as 'root'.

The reason an executable would be run as 'root' is so that it can modify specific files that the user would not normally be allowed to, without giving the user full root access.

A default use of this can be seen with the <code>/usr/bin/passwd</code> binary file. <code>/usr/bin/passwd</code> needs to modify <code>/etc/passwd</code> and <code>/etc/shadow</code> which store account information and password hashes for all users, and these can only be modified by the user 'root'.<syntaxhighlight lang="console">
[ thompson ~ ] $ stat -c "%a %U:%G %n" /usr/bin/passwd
4701 root:root /usr/bin/passwd

[ thompson ~ ] $ passwd
passwd: Changing password for thompson
</syntaxhighlight>

The owner of the process is not the user running the executable file but the owner of the executable file