Arch Linux

rnabioullin

Member

Registered: 2010-10-02

Posts: 24

"System User" and "System Group" Definition

What exactly is a "system user" and "system group"? Does it correspond to a specific application (e.g., mysql, ntp, dbus), a capability (e.g., wheel, audio, disk), neither, or both? If it does correspond to a specific application or capability, why are the UIDs and GIDs of these users and groups, respectively, lower than SYS_UID_MIN and SYS_GID_MIN (defined in /etc/login.defs), respectively?

vcap

Member

Registered: 2009-09-10

Posts: 9

Re: "System User" and "System Group" Definition

When using useradd without the-u/--uid option it will pick a free UID in the range:

• SYS_UID_MIN..SYS_UID_MAX if -r/--system option is present

• UID_MIN..UID_MAX otherwise

(respectively with groupadd, -g/--gid, GID).

and apparently Arch has a policy of using number below SYS_{UID,GID}_MIN for distro provided accounts.

that's really all there is to it. it's mostly a matter of convention (only uid/gid 0 are truly special, afaict).

Last edited by vcap (2011-09-06 15:12:47)