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