Start N Stop Linux System

halt command


shutdown the system instantly
It instructs the hardware to stop all CPU functions but leaves it powered on.

  • -p power-off the machine
  • –reboot reboot the machine

shutdown [OPTION] [TIME] [MESSAGE]

shutdown -h now

reboot command

For graceful shutdown and restart of the machine.

  • -p poweroff
  • -f Reboot forcibly
  • –halt halt the machine
  • –verbose Outputs slightly more verbose messages, useful for debugging problems with shutdown.

Reboot in next 15 minutes

shutdown -r +15

Reboot Now

shutdown -r now

The Kernel loads the /sbin/reboot and /sbin/shutdown binaries from the disk and execute them. If it fails due to a problem with the drive, generates an error like:
bash: /sbin/reboot: Input/output error
shutdown -r now

bash: /sbin/shutdown: Input/output error

On the next boot, an fsck would correct whatever is wrong with the disk.

poweroff command

Sends an ACPI signal which instructs the system to power down.


–halt halt the machine
–reboot reboot the machine

Suspend & Hibernate Command

Suspend & Hibernate


Suspends Systems


Hibernate System


init command

Init with run level 6 is set for rebooting

init 6


/sbin/init 6

init 0   shutdown the Linux System

Reboot logs


contains records all logins and logouts.

Use the command to parse this file

last reboot

Disable Shutdown and Reboot for specific users or group

vi /etc/sudoers

Add these lines to the Command Aliases section.

Cmnd_Alias SHUTDOWN = /sbin/shutdown,/sbin/reboot,/sbin/halt,/sbin/poweroff

# User privilege specification

# Allow members of group sudo to execute any command
%developers ALL=(ALL:ALL) ALL, !SHUTDOWN

Another way is to remove execution permissions on shutdown and reboot commands for all users except root.

chmod o-x /sbin/shutdown
chmod o-x /sbin/reboot
chmod o-x /bin/systemctl

Seldom Reboot on Servers Satisfying Linux System Administrators

Linux 4.0 enabled servers like Oracle Linux, and RHEL can go without reboot for years with Ksplice.
Red Hat kpatch and SUSE kGraft, provides the Linux to keep running even while critical patches installed.
Kpatch issues a stop_machine() command and looks at the stack of existing processes using ftrace to patch safely. Further, it redirects the running code to the patched functions and then removes the now outdated code.