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--- linux_wiki:init_systems [2015/08/13 21:57]
billdozor [rc#.d directories]
+++ linux_wiki:init_systems [2019/05/25 23:50]
@@ Line 1: / Line 1: @@
-====== Init Systems ======
-**General Information**
-Down and dirty quick info about three different init systems that Linux uses; SysV init, upstart, and systemd.
-**Checklist**
-  * Distro: Varies, depending upon init system.
-----
-===== All Inits =====
-This section will compare three init systems; sysv, upstart, and systemd.
-==== Command Table ====
-  * The service name "foo" will be used in all examples.
-  * systemctl assumes ".service" appended to unit name if left off
-^ Command ^ Sysv ^ Upstart ^ Systemd ^
-| Status of Service | service foo status | initctl status foo | systemctl status foo |
-| Start Service | service foo start | initctl start foo | systemctl start foo |
-| Stop Service | service foo stop | initctl stop foo | systemctl stop foo |
-| Restart Service | service foo restart | initctl restart foo | systemctl restart foo |
-| Reload config file | service foo reload | initctl reload foo | systemctl reload foo |
-| List services | ls /etc/init.d/ | initctl list | systemctl (or)\\ systemctl list-unit-files (or)\\ systemctl list-unit-files --type=service |
-| Enable Service At Boot | chkconfig foo on | Edit /etc/init/<jobname>.conf "start on" field | systemctl enable foo |
-| Disable Service At Boot | chkconfig foo off | Edit /etc/init/<jobname>.conf "start on" field | systemctl disable foo |
-| List services and enabled run levels | chkconfig --list | initctl show-config | systemctl list-unit-files --type=service (or)\\ ls /etc/systemd/system/*.wants/ |
-----
-==== All Inits Run Levels ====
-^ Description ^ Sysv ^ Upstart ^ Systemd ^
-| Halt system | 0 | runlevel [0] | poweroff.target |
-| Single user mode | 1,s,single | runlevel [1] | rescue.target |
-| User defined. Same as 3 by default. | 2,4 | runlevel [24] | multi-user.target |
-| Multi-user, non-graphical | 3 | runlevel [3] | multi-user.target |
-| Multi-user, graphical | 5 | runlevel [5] | graphical.target |
-| Reboot | 6 | runlevel [6] | reboot.target |
-| Emergency shell | emergency | ? | emergency.target |
-  * Note: Upstart has many different "events" besides runlevels that can trigger jobs to start, such as "start on file-system" or "start on startup"
-----
-===== SysV Init (init) =====
-Sysv init details not contained in All Inits section.
-__Distributions__: RHEL/CentOS <= 6 (RHEL 6 uses an init/upstart combination), Debian <= 7
-==== Defualt run level ====
-  * Set in file: /etc/inittab
-Example with run level 5 as default:
-<code bash>
-id:5:initdefault
-</code>
-==== Master Copy of Startup Scripts ====
-/etc/rc.d/init.d/
-==== rc#.d directories ====
-The rc#.d directories contain symbolic links to the scripts in /etc/rc.d/init.d.
-# = the run level, ie rc0.d, rc1.d, rc2.d, rc3.d, rc4.d, rc5.d, rc6.d
-__Locations__
-  * /etc/rc.d/rc#.d or
-  * /etc/rc#.d
-__Script Names__
-  * Scripts are named for if they are going to Start(S) or Kill(K) the script, a sequence number, and then the name of the script.
-  * /etc/rc2.d/S80cups  = This would Start(S) cups after any scripts numbered S01 to S79
-  * /etc/rc0.d/K80cups  = This would Stop/Kill (K) cups after any scripts numbered K01 to K79
-==== Manage Services ====
-  * service command: RedHat and Debian (service status/stop/start/restart)
-  * chkconfig: Red Hat based systems (enable/disable services)
-  * update-rc.d: Debian/Ubuntu (enable/disable services)
-----
-===== Upstart =====
-Upstart details not contained in All Inits section.
-__Distributions__: Ubuntu 9.10 - Current (migrating to systemd), RHEL/CentOS 6 (some scripts)
-Upstart uses event driven jobs, instead of run levels to executes scripts.
-It does have events for rc0-6 to maintain compatibility with init.
-  * Job Definition Files Location: /etc/init/
-  * Job control: initctl
-----
-===== Systemd =====
-Systemd details not contained in All Inits section.
-__Distributions__: RHEL/CentOS 7, Debian 8, Ubuntu 15.4?
-==== Location of Unit Scripts ====
-  * All of systemd unit scripts are located here (and sub folders): /usr/lib/systemd/
-  * Systemd uses this directory of symlinks to run those scripts: /etc/systemd/system/
-  * Other systemd configuration: /etc/systemd/
-  * Unit control: systemctl
-==== Laptop: Disable Suspend ====
-On systemd based systems, the laptop suspend on lid closed can be disabled by changing the logind config.
-) Edit /etc/systemd/logind.conf
-) Uncomment "HandleLidSwitch" and set to ignore
-<code bash>
-HandleLidSwitch=ignore
-</code>