In Linux system administration, it is sometimes required to restart our server after the completion of some network and other major updates either relevant to software or hardware that are being carried on the server. The reboot is needed so that the changes that we have done can be affected on the server. For example, if we are re-compiling the server’s kernel that undergoes some more advanced server administration, we have to restart the machine in order to complete the compilation and have a new updated kernel version on the server. Updating server’s memory, IP allocation, NIC configuration are the key tasks that need to have server restarted once leading to their successful implementation.
Most of the Linux system administrators do access the servers via shell or SSH to perform administrative activities, server management and monitoring. So they need to know the basic commands to restart the server from shell.
This article covers various restart commands and options such as
1. Where to find help regarding restarting your system.
2. How to restart your system.
3. How to schedule/cancel a restart.
4. How to remotely restart your server.
5. Restart with Init Command.
6. Checking reboot logs.
Restart your system
If all you need is a restart without going into details just help yourself with one of the following commands:
#sudo shutdown –r now
Note: usage of reboot, halt and poweroff is similar in syntax and effect. Run each command with –help to see the details.
Simple reboot command has limited usage. Shutdown command is used instead of reboot for much more advance reboot and shutdown requirements. One such situation is a scheduled restart. Following is the syntax used to reboot your system after time defines by TIME.
#sudo shutdown –r [TIME] [MESSAGE]
Here TIME has various formats. Simplest one is “now”, already listed in previous section, and tells system to restart immediately. Other valid formats are +m, where m is the number of minutes to wait until restart and HH:MM which specifies the TIME in 24hr clock. Below are the examples and their outputs. Optional MESSAGE argument can be use to intimate users prior to reboot to prevent possible loss of data.
Reboot your system after 5 minutes
#sudo shutdown –r +5
Broadcast message from [email protected]
(/dev/pts/1) at 20:49 ...
The system is going down for reboot in 5 minutes!
Reboot your system after 02:00 A.M
#sudo shutdown –r 02:00
Broadcast message from [email protected]
(/dev/pts/1) at 20:51 ...
The system is going down for reboot in 309 minutes!
If you want your system to discard previously scheduled restart or shutdown you can call another shutdown command with –c option and broadcast with it a message for users about the cancelation of restart. Here is the syntax and example
#sudo shutdown –c [MESSAGE]
The previously scheduled reboot can be cancelled by system administrator by issuing another shutdown command with –c option and optional message argument.
#sudo shutdown –c “showing how to cancel scheduled reboot ”
Broadcast message from m[email protected]
(/dev/pts/1) at 20:59 ...
showing how to cancel scheduled reboot
Restart remote server
Simply login your server with any ssh client using server authentication information and issue any of the following commands:
Restart with Init Command
Init is taken from the word initialize that is widely used to initialize/start different processes in a linux server, so this command used as a joint with runlevel 6; a number which is set for rebooting a linux server leads to get the server rebooted. The syntax is mentioned below:
[[email protected] ~]# init 6
[[email protected] ~]# /sbin/init 6
Checking reboot logs
/var/log/wtmp file records all logins and logouts. One can parse this file with last command in order to access log for reboot. Below is the last command usage and its output on my system.
reboot system boot 3.2.0-32-generic Sun Nov 4 11:00 - 22:11 (11:11)
reboot system boot 3.2.0-32-generic Sat Nov 3 20:02 - 02:10 (06:08)
reboot system boot 3.2.0-32-generic Sat Nov 3 17:52 - 18:56 (01:03)
reboot system boot 3.2.0-32-generic Sat Nov 3 15:37 - 17:32 (01:55)
reboot system boot 3.2.0-32-generic Sat Nov 3 11:00 - 11:02 (00:01)
reboot system boot 3.2.0-32-generic Sat Nov 3 10:25 - 10:58 (00:32)
reboot system boot 3.2.0-32-generic Fri Nov 2 20:21 - 23:25 (03:04)
reboot system boot 3.2.0-32-generic Fri Nov 2 16:57 - 18:54 (01:56)
reboot system boot 3.2.0-32-generic Fri Nov 2 15:22 - 16:35 (01:13)
reboot system boot 3.2.0-32-generic Fri Nov 2 12:51 - 13:37 (00:46)
reboot system boot 3.2.0-32-generic Thu Nov 1 20:04 - 23:55 (03:50)
reboot system boot 3.2.0-32-generic Thu Nov 1 15:18 - 23:55 (08:36)
reboot system boot 3.2.0-32-generic Thu Nov 1 11:42 - 13:59 (02:16)
wtmp begins Thu Nov 1 11:31:44 2012
Thanks for reading this article and please which your favorite reboot command?
- How to Schedule shutdown, restart, hibernate and log off Tasks in Linux
- 4 Commands to Shutdown Linux from Terminal