Linux:SystemGroups
리눅스의 잘 알려진 시스템 그룹들.
Groups without an associated user
The following groups grant privileges to their members.
- lp (LP): Members of this group can enable and use printers. (The user lp is not used anymore.)
- lpadmin (LPADMIN): Allows members to manage printers and pending jobs sent by other users.
- scanner : Members of this group can enable and use scanners.
- adm: Group adm is used for system monitoring tasks. Members of this group can read many log files in /var/log, and can use xconsole. Historically, /var/log was /usr/adm (and later /var/adm), thus the name of the group.
- systemd-journal: Since Debian 8 (Jessie), members of this group can use the command journalctl and read log files of systemd (in /var/log/journal).
- plugdev: Allows members to mount (only with the options nodev and nosuid, for security reasons) and umount removable devices through pmount.
- netdev: Members of this group can manage network interfaces through the network manager and wicd.
- cdrom: This group can be used locally to give a set of users access to a CDROM drive and other optical drives.
- floppy: This group can be used locally to give a set of users access to a floppy drive and other removable (non-optical) drives (like USB flash drives). Starting with Debian 8 (Jessie) it is not used anymore for USB and flash memories.
- tape: This group can be used locally to give a set of users access to a tape drive.
- audio: This group can be used locally to give a set of users access to an audio device (the soundcard or a microphone).
- video: This group can be used locally to give a set of users access to a video device (like a webcam).
- render: This group can be used locally to give a set of users access to a rendering device (like the framebuffer, or videocard).
- sudo: Members of this group can execute any command with sudo or pkexec. (See the default configuration in /etc/sudoers)
- tty: TTY devices are owned by this group. This is used by write and wall to enable them to write to other people's TTYs, but it is not intended to be used directly.
- staff: Allows users to add local modifications to the system (/usr/local) without needing root privileges (note that executables in /usr/local/bin are in the PATH variable of any user, and they may "override" the executables in /bin and /usr/bin with the same name). Compare with group "adm", which is more related to monitoring/security.
- shadow: /etc/shadow is readable by this group. Some programs that need to be able to access the file are SETGID shadow.
- utmp: This group can write to /var/run/utmp and similar files. Programs that need to be able to write to it are SETGID utmp.
- disk: Raw access to disks. Mostly equivalent to root access.
- kmem: /dev/mem and /dev/port are readable by this group. This is mostly a BSD relic, but any programs that need direct read access to the system's memory can thus be made SETGID kmem. /dev/kmem, that has given the name to this group, was also readable by this group, but is currently disabled by default for security reasons.
- dialout: Full and direct access to serial ports. Members of this group can reconfigure the modem, dial anywhere, etc.
- dip: The group's name stands for "Dial-up IP", and membership in dip allows you to use tools like ppp, dip, wvdial, etc. to dial up a connection. The users in this group cannot configure the modem, but may run the programs that make use of it.
- fax: Allows members to use fax software to send / receive faxes.
- voice: Voicemail, useful for systems that use modems as answering machines.
- users: While Debian systems use the private user group system by default (each user has their own group), some prefer to use a more traditional group system, in which each user is a member of this group.
- wheel: This group can be created to alter the functionality of the module pam_wheel in /etc/pam.d/su to restrict the execution of su. If this group does not exists only members of root (usually root itself) are affected. By default this group does not exist and all the configurations with pam_wheel are commented in /etc/pam.d/su. See the page about the wheel_pam module for more information.
- src: This group was used to manage the source code of the system, including files in /usr/src. It is not used anymore.
- bluetooth: Users in this group can talk with bluetooth service via dbus, as defined in /etc/dbus-1/system.d/bluetooth.conf.
- libvirt: Users in this group can talk with libvirt service via dbus, as defined in /etc/libvirt/libvirtd.conf.
- kvm: Users in this group can use the KVM acceleration of virtual machines.
Groups with an associated user
The following groups are not intended to be used directly by other users.
- root: Root is (typically) the superuser.
- daemon: Some unprivileged daemons that need to write to files on disk run as daemon.daemon (e.g., portmap, atd, probably others). Daemons that don't need to own any files can run as nobody.nogroup instead, and more complex or security conscious daemons run as dedicated users. The daemon user is also handy for locally installed daemons.
- games: Many games are SETGID to games so they can write their high score files. This is explained in policy.
- man: The man program (sometimes) runs as user man, so it can write cat pages to /var/cache/man.
- mail: Mailboxes in /var/mail are owned by group mail, as explained in policy. The user and group are used for other purposes by various MTA's as well.
- news: Various news servers and other associated programs (such as suck) use user and group news in various ways. Files in the news spool are often owned by user and group news. Programs such as inews that can be used to post news are typically SETGID news.
- proxy: Like daemon, this user and group is used by some daemons (specifically, proxy daemons) that don't have dedicated user id's and that need to own files. For example, group proxy is used by pdnsd, and squid runs as user proxy.
- postgres: Postgresql databases are owned by this user and group. All files in /var/lib/postgresql are owned by this user to enforce proper security.
- www-data: Some web servers run as www-data. Web content should not be owned by this user, or a compromised web server would be able to rewrite a web site. Data written out by web servers, including log files, will be owned by www-data.
- backup: So backup/restore responsibilities can be locally delegated to someone without full root permissions.
- list: Mailing list archives and data are owned by this user and group. Some mailing list programs may run as this user as well.
- irc: Used by irc daemons. A statically allocated user is needed only because of a bug in ircd, which SETUID()s itself to a given UID on startup.
- sync: The shell of user sync is /bin/sync. Thus, if its password is set to something easy to guess (such as ""), anyone can sync the system at the console even if they don't have an account.
- uucp: The uucp user and group is used by the UUCP subsystem. It owns spool and configuration files. Users in the uucp group may run uucico.
- operator: Operator was (historically) the only 'user' account that could login remotely.
- bin: maintained for historic reasons.
- sys: same as with bin.
- nogroup (user: nobody): Daemons that need not own any files run as user nobody and group nogroup. Thus, no files on a system should be owned by this user or group.