From 89df7fa33f5d6f013f616cc79bdb3f5c6d37905b Mon Sep 17 00:00:00 2001 From: darksun Date: Sun, 5 May 2019 10:27:20 +0800 Subject: [PATCH] =?UTF-8?q?=E9=80=89=E9=A2=98:=2020190505=20Five=20Methods?= =?UTF-8?q?=20To=20Check=20Your=20Current=20Runlevel=20In=20Linux=3F=20sou?= =?UTF-8?q?rces/tech/20190505=20Five=20Methods=20To=20Check=20Your=20Curre?= =?UTF-8?q?nt=20Runlevel=20In=20Linux.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...To Check Your Current Runlevel In Linux.md | 183 ++++++++++++++++++ 1 file changed, 183 insertions(+) create mode 100644 sources/tech/20190505 Five Methods To Check Your Current Runlevel In Linux.md diff --git a/sources/tech/20190505 Five Methods To Check Your Current Runlevel In Linux.md b/sources/tech/20190505 Five Methods To Check Your Current Runlevel In Linux.md new file mode 100644 index 0000000000..2169f04e51 --- /dev/null +++ b/sources/tech/20190505 Five Methods To Check Your Current Runlevel In Linux.md @@ -0,0 +1,183 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Five Methods To Check Your Current Runlevel In Linux?) +[#]: via: (https://www.2daygeek.com/check-current-runlevel-in-linux/) +[#]: author: (Magesh Maruthamuthu https://www.2daygeek.com/author/magesh/) + +Five Methods To Check Your Current Runlevel In Linux? +====== + +A run level is an operating system state on Linux system. + +There are seven runlevels exist, numbered from zero to six. + +A system can be booted into any of the given runlevel. Run levels are identified by numbers. + +Each runlevel designates a different system configuration and allows access to a different combination of processes. + +By default Linux boots either to runlevel 3 or to runlevel 5. + +Only one runlevel is executed at a time on startup. It doesn’t execute one after another. + +The default runlevel for a system is specified in the /etc/inittab file for SysVinit system. + +But systemd systems doesn’t read this file and it uses the following file `/etc/systemd/system/default.target` to get default runlevel information. + +We can check the Linux system current runlevel using the below five methods. + + * **`runlevel Command:`** runlevel prints the previous and current runlevel of the system. + * **`who Command:`** Print information about users who are currently logged in. It will print the runlevel information with “-r” option. + * **`systemctl Command:`** It controls the systemd system and service manager. + * **`Using /etc/inittab File:`** The default runlevel for a system is specified in the /etc/inittab file for SysVinit System. + * **`Using /etc/systemd/system/default.target File:`** The default runlevel for a system is specified in the /etc/systemd/system/default.target file for systemd System. + + + +Detailed runlevels information is described in the below table. + +**Runlevel** | **SysVinit System** | **systemd System** +---|---|--- +0 | Shutdown or Halt the system | shutdown.target +1 | Single user mode | rescue.target +2 | Multiuser, without NFS | multi-user.target +3 | Full multiuser mode | multi-user.target +4 | unused | multi-user.target +5 | X11 (Graphical User Interface) | graphical.target +6 | reboot the system | reboot.target + +The system will execute the programs/service based on the runlevel. + +For SysVinit system, it will be execute from the following location. + + * Run level 0 – /etc/rc.d/rc0.d/ + * Run level 1 – /etc/rc.d/rc1.d/ + * Run level 2 – /etc/rc.d/rc2.d/ + * Run level 3 – /etc/rc.d/rc3.d/ + * Run level 4 – /etc/rc.d/rc4.d/ + * Run level 5 – /etc/rc.d/rc5.d/ + * Run level 6 – /etc/rc.d/rc6.d/ + + + +For systemd system, it will be execute from the following location. + + * runlevel1.target – /etc/systemd/system/rescue.target + * runlevel2.target – /etc/systemd/system/multi-user.target.wants + * runlevel3.target – /etc/systemd/system/multi-user.target.wants + * runlevel4.target – /etc/systemd/system/multi-user.target.wants + * runlevel5.target – /etc/systemd/system/graphical.target.wants + + + +### 1) How To Check Your Current Runlevel In Linux Using runlevel Command? + +runlevel prints the previous and current runlevel of the system. + +``` +$ runlevel +N 5 +``` + + * **`N:`** “N” indicates that the runlevel has not been changed since the system was booted. + * **`5:`** “5” indicates the current runlevel of the system. + + + +### 2) How To Check Your Current Runlevel In Linux Using who Command? + +Print information about users who are currently logged in. It will print the runlevel information with `-r` option. + +``` +$ who -r + run-level 5 2019-04-22 09:32 +``` + +### 3) How To Check Your Current Runlevel In Linux Using systemctl Command? + +systemctl is used to controls the systemd system and service manager. systemd is system and service manager for Unix like operating systems. + +It can work as a drop-in replacement for sysvinit system. systemd is the first process get started by kernel and holding PID 1. + +systemd uses `.service` files Instead of bash scripts (SysVinit uses). systemd sorts all daemons into their own Linux cgroups and you can see the system hierarchy by exploring `/cgroup/systemd` file. + +``` +$ systemctl get-default +graphical.target +``` + +### 4) How To Check Your Current Runlevel In Linux Using /etc/inittab File? + +The default runlevel for a system is specified in the /etc/inittab file for SysVinit System but systemd systemd doesn’t read the files. + +So, it will work only on SysVinit system and not in systemd system. + +``` +$ cat /etc/inittab +# inittab is only used by upstart for the default runlevel. +# +# ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM. +# +# System initialization is started by /etc/init/rcS.conf +# +# Individual runlevels are started by /etc/init/rc.conf +# +# Ctrl-Alt-Delete is handled by /etc/init/control-alt-delete.conf +# +# Terminal gettys are handled by /etc/init/tty.conf and /etc/init/serial.conf, +# with configuration in /etc/sysconfig/init. +# +# For information on how to write upstart event handlers, or how +# upstart works, see init(5), init(8), and initctl(8). +# +# Default runlevel. The runlevels used are: +# 0 - halt (Do NOT set initdefault to this) +# 1 - Single user mode +# 2 - Multiuser, without NFS (The same as 3, if you do not have networking) +# 3 - Full multiuser mode +# 4 - unused +# 5 - X11 +# 6 - reboot (Do NOT set initdefault to this) +# +id:5:initdefault: +``` + +### 5) How To Check Your Current Runlevel In Linux Using /etc/systemd/system/default.target File? + +The default runlevel for a system is specified in the /etc/systemd/system/default.target file for systemd System. + +It doesn’t work on SysVinit system. + +``` +$ cat /etc/systemd/system/default.target +# This file is part of systemd. +# +# systemd is free software; you can redistribute it and/or modify it +# under the terms of the GNU Lesser General Public License as published by +# the Free Software Foundation; either version 2.1 of the License, or +# (at your option) any later version. + +[Unit] +Description=Graphical Interface +Documentation=man:systemd.special(7) +Requires=multi-user.target +Wants=display-manager.service +Conflicts=rescue.service rescue.target +After=multi-user.target rescue.service rescue.target display-manager.service +AllowIsolate=yes +``` +-------------------------------------------------------------------------------- + +via: https://www.2daygeek.com/check-current-runlevel-in-linux/ + +作者：[Magesh Maruthamuthu][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.2daygeek.com/author/magesh/ +[b]: https://github.com/lujun9972