| Red Hat Linux 7.3: The Official Red Hat Linux Reference Guide | ||
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Red Hat Linux allows the first privileged user to log in on the physical console of the machine the ability to manipulate devices and perform tasks normally reserved for root. This is done through a PAM module called pam_console.so.
When a user logs into a machine under Red Hat Linux, the pam_console.so module is called by login or the graphical login program, gdm. If this user is the first user to log in at the physical console — called the console user — the module grants ownership of a variety of devices normally owned by root. The console user owns these devices until the last local session for that user ends. Once the user has logged out, ownership of the devices reverts back to their default values.
The devices affected include, but are not limited to, sound cards, floppy drives, and CD-ROM drives.
This allows a local user to manipulate these devices without attaining root, thus simplifying common tasks for the console user.
You can edit the list of devices controlled by pam_console.so in the file /etc/security/console.perms.
The console user is also allowed access to any program with a file bearing the command name in the /etc/security/console.apps/ directory. These files do not need to contain any data, but must have the exact name of the to which command they correspond.
One notable group of applications the console user has access to are three programs which shut off or reboot the system. These are:
/sbin/halt
/sbin/reboot
/sbin/poweroff
Because these are PAM-aware applications, they call the pam_console.so as a requirement for use.
For more information see the man pages for pam_console, console.perms, and console.apps.