For an immediate, orderly restart on Ubuntu 18.04 Desktop or Server, run:
sudo rebootYou need administrative privileges. The command requests a normal system shutdown and reboot; services are stopped, storage is handled by the system manager, local terminals close, and SSH sessions disconnect. Reconnect after the host finishes starting.
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Restart Ubuntu 18.04 immediately
Ubuntu 18.04 uses systemd. Its reboot command preserves traditional compatibility, while systemd provides the explicit systemctl reboot operation (Ubuntu 18.04 reboot manual).
sudo rebootThis is the shortest standard command for most users. The explicit systemd form is:
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sudo systemctl rebootYou can also use the shutdown command with an explicit immediate time:
sudo shutdown -r nowHere, -r means reboot and now means do it immediately. Use now whenever an immediate restart is intended; do not rely on an omitted time argument.
Which command should you choose?
| Command | Best use |
|---|---|
sudo reboot |
Simple, immediate restart |
sudo systemctl reboot |
Explicit systemd wording in administration runbooks |
sudo shutdown -r now |
Immediate restart using the shutdown command family |
sudo shutdown -r +5 |
Restart after a delay |
sudo shutdown -r +5 "message" |
Delayed restart with a warning to logged-in users |
init 6 may appear in older documentation, but it is legacy compatibility terminology rather than the preferred Ubuntu 18.04 example.
Schedule a reboot
After a number of minutes
sudo shutdown -r +10This schedules a reboot 10 minutes from the time the command is accepted.
At a clock time
sudo shutdown -r 23:30The clock-time form uses the machine’s local time. Confirm the server’s timezone if it runs on UTC or another timezone.
Send a warning
sudo shutdown -r +10 "System will restart in 10 minutes for maintenance."The message is broadcast to logged-in users. A time argument such as now, +10, or 23:30 must come before the message. On multi-user systems, a scheduled shutdown can create /run/nologin shortly before the operation so that new logins are refused. See the systemd shutdown manual for the command’s time, message, and cancellation syntax.
Cancel a scheduled reboot
sudo shutdown -cThis cancels a pending shutdown or reboot that was scheduled for a future time. It cannot undo a reboot already started with now or an operation that is already shutting the system down. The shutdown --show option belongs to later systemd versions, so do not assume it is available on Ubuntu 18.04; use man shutdown to inspect the installed command.
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Restart Ubuntu over SSH
Run the same command from the remote shell:
sudo rebootThe SSH connection normally terminates as soon as the remote host begins rebooting. That disconnect is expected and does not by itself indicate failure. Wait for the machine to return, then reconnect. Before rebooting a remote server, make sure you have a physical console, virtual-machine console, cloud serial or web console, IPMI, or another recovery path in case networking or boot fails. Do not repeatedly issue reboot commands merely because the current SSH session closed.
What happens during a normal reboot?
- The command requests a system shutdown and restart.
- systemd stops services and performs the normal shutdown handling.
- Filesystems and storage are processed by the system manager.
- The machine starts the operating system again.
- Local terminals close and remote sessions disconnect.
- Users reconnect when services and networking are available.
There is no universal reboot duration. Hardware, running services, disk checks, virtual-machine infrastructure, cloud-provider behavior, and failed services all affect the time.
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If a reboot command fails
Permission denied or authentication failure
Ordinary users normally need sudo:
sudo rebootA root shell can omit sudo. If your account is not authorized in sudoers, an administrator must grant the privilege or perform the restart.
“Command not found”
Check whether the commands are on the path:
command -v reboot
command -v systemctlThey are normally present on a standard Ubuntu 18.04 installation. If sudo is unavailable, switch to a root shell or use the system’s approved administrative access method. For complete syntax and locally installed behavior, read:
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man reboot
man shutdown
man systemctlUbuntu’s command-line reference also recommends man <command> for command details (Ubuntu CLI cheatsheet).
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The host does not return
Possible causes include a service hanging during shutdown, a filesystem or disk problem, failed network configuration, a virtual-machine or hypervisor issue, or a kernel or hardware fault. Use a physical or virtual console, cloud-provider serial/web console, remote-management controller, or provider-side restart when operating-system recovery is unavailable.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When Ubuntu is frozen: emergency force reboot
Try a normal reboot and a console or out-of-band recovery method first. Ubuntu 18.04 documents this emergency form:
sudo reboot -fThe -f option forces an immediate halt, poweroff, or reboot and can bypass normal service cleanup. Use it only when the system is unresponsive and a controlled reboot cannot be completed. It can leave applications and filesystems without their normal shutdown handling, increasing the risk of data loss or filesystem damage. Do not use it just because a normal reboot takes several seconds, and do not treat repeated force options such as -ff as routine administration.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11If the reboot has already begun, cancellation is generally too late; sudo shutdown -c applies only while a future scheduled operation is still pending.
Reboot, shutdown, halt, and poweroff
- Reboot/restart: stops the operating system and starts it again.
- Shutdown: a general command that can halt, power off, or reboot depending on its options.
- Halt: stops the operating system; it is not necessarily the same as removing power from the hardware.
- Poweroff: shuts down the operating system and turns the machine off.
For a restart, use sudo reboot, sudo systemctl reboot, or sudo shutdown -r now. Do not substitute:
sudo poweroffThat command powers the machine off rather than starting it again.
Quick Recap
Quick command reference
| Task | Command |
|---|---|
| Immediate restart | sudo reboot |
| Explicit systemd restart | sudo systemctl reboot |
| Immediate shutdown-command restart | sudo shutdown -r now |
| Restart in five minutes | sudo shutdown -r +5 |
| Restart at 02:00 local time | sudo shutdown -r 02:00 |
| Warn users and restart in 15 minutes | sudo shutdown -r +15 "Rebooting in 15 minutes for scheduled maintenance." |
| Cancel a pending scheduled restart | sudo shutdown -c |
| Emergency force reboot | sudo reboot -f |
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