Overview
Simply cutting power when shutting down a system can lead to data corruption or file system errors. `shutdown` is essential in server environments because it safely terminates all running processes, logs events, and then shuts down the system.
Key Features
Key features of the `shutdown` command include:
- Ability to schedule system shutdown/reboot at a specified time
- Sends shutdown notification messages to all logged-in users
- Synchronizes file systems and gracefully terminates processes
- Supports both immediate and scheduled shutdowns
Shutdown Types
The `shutdown` command supports various shutdown methods.
- Halt: Shuts down the system but does not power it off, leaving it in a suspended state.
- Poweroff: Completely shuts down the system and turns off the power. In most cases, it behaves identically to the 'shutdown -h' option.
- Reboot: Shuts down the system and then immediately restarts it.
Key Options
Commonly used `shutdown` command options are grouped by purpose.
1) Shutdown/Reboot
2) Time and Message
3) Help
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Description:
`shutdown` Executes the command.
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Usage Examples
Learn the functionalities of the `shutdown` command through various usage examples.
Immediate System Shutdown
sudo shutdown -h nowShuts down the system immediately without delay and powers it off. Uses the 'now' keyword.
Reboot System in 10 Minutes
sudo shutdown -r +10Reboots the system 10 minutes from the current time. Uses the '-r' option for reboot and '+10' for 10 minutes later.
Reboot at Specific Time with Message
sudo shutdown -r 22:30 "Regular system maintenance will be performed."Reboots the system today at 22:30, sending a maintenance message to all logged-in users.
Cancel Scheduled Shutdown
sudo shutdown -cCancels a pending `shutdown` command. A notification is sent to all users at the time of cancellation.
Installation
The `shutdown` command is typically included by default in most Linux distributions. No separate installation is required.
Tips & Cautions
Here are some points to keep in mind when using the `shutdown` command.
Tips
- The `shutdown` command requires root privileges, so it should be used with 'sudo'.
- `shutdown -h now` and `poweroff` behave almost identically, but `shutdown` is safer as it allows time for processes to terminate gracefully.
- If the `shutdown` command does not work, you can use 'init 0' (for shutdown) or 'init 6' (for reboot). However, these commands may not be as safe as `shutdown`.
- To cancel a scheduled shutdown, you must use 'shutdown -c'.