When using the new RHEL 7.2 release and running the systemctl status command, some slight changes were recently visible:
# systemctl status sshd ● sshd.service - OpenSSH server daemon Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled) Active: active (running) since Sat 2016-02-13 10:56:40 CET; 6s ago Docs: man:sshd(8) man:sshd_config(5) Main PID: 1286 (sshd) CGroup: /system.slice/sshd.service └─1286 /usr/sbin/sshd -D Feb 13 10:56:40 server.example.com systemd[1]: Started OpenSSH server daemon. Feb 13 10:56:40 server.example.com systemd[1]: Starting OpenSSH server daem.... Feb 13 10:56:40 server.example.com sshd[1286]: Server listening on 0.0.0.0 .... Feb 13 10:56:40 server.example.com sshd[1286]: Server listening on :: port 22. Feb 13 10:56:44 server.example.com sshd[2457]: Accepted password for root f...2 Hint: Some lines were ellipsized, use -l to show in full.
As you can see above, a new string vendor preset: enabled is now displayed. Here it means that the preset mechanism has been applied on the sshd package.
The preset mechanism came with Systemd and the RHEL 7.0 release, the RHEL 7.2 release just makes it visible. It is a way for a Linux distribution (Debian, CentOS, etc) to centrally define whether a package should be automatically enabled or not at installation time.
So, through the well known directory hierarchy (/usr/lib/systemd/system-preset, /etc/systemd/system-preset, /run/systemd/system-preset), a Linux distribution can specify how packages initially behave.
A typical preset file would appear like this:
# more /usr/lib/systemd/system-preset/90-default.preset # System stuff enable sshd.service enable atd.* enable crond.* enable chronyd.service enable rpcbind.* enable NetworkManager.service enable NetworkManager-dispatcher.service enable ModemManager.service enable auditd.service enable restorecond.service enable bluetooth.* enable avahi-daemon.* enable cups.* # The various syslog implementations enable rsyslog.* enable syslog-ng.* enable sysklogd.* # Network facing enable firewalld.service enable libvirtd.service enable xinetd.service enable ladvd.service ...
A directive enable or disable precedes each package in this file as appropriate.
You shouldn’t need to modify this file in most cases but it is still interesting to know that it exists.
Sources: systemd.preset man page and Freedesktop.org website.
Recent Comments