System Automatic Restart

Method 1: Using Cron Jobs (Recurring Restarts)

Cron jobs allow you to schedule commands to run at specified intervals.

Setting Up a Daily Restart at 3:00 AM

# Edit the crontab file
sudo crontab -e

# Add this line to restart daily at 3:00 AM
0 3 * * * /sbin/shutdown -r now

Common Cron Schedule Patterns

Schedule	Cron Expression	Description
Daily at 1:00 AM	`0 1 * * * /sbin/shutdown -r now`	Restarts every day at 1:00 AM
Every Sunday at 4:00 AM	`0 4 * * 0 /sbin/shutdown -r now`	Restarts weekly on Sundays
Every 6 hours	`0 /6 * * /sbin/shutdown -r now`	Restarts every 6 hours

Cron Format Explained

MIN HOUR DAY MONTH DAYOFWEEK COMMAND

MIN: Minute (0-59)
HOUR: Hour (0-23)
DAY: Day of month (1-31)
MONTH: Month (1-12)
DAYOFWEEK: Day of week (0-6, where 0 is Sunday)
COMMAND: Command to execute

Method 2: One-Time Scheduled Restart

To schedule a one-time restart:

# Restart 24 hours from now
sudo shutdown -r +1440

# Restart at a specific time today
sudo shutdown -r 23:00

# Cancel a scheduled restart
sudo shutdown -c

Checking Scheduled Shutdowns/Restarts

# Check if a shutdown/restart is scheduled
cat /run/systemd/shutdown/scheduled

# Cancel a scheduled shutdown/restart
sudo shutdown -c

# Schedule a restart at specific time (e.g., 11:00 PM)
# sudo shutdown -r 23:00

# view the scheduled shutdown if there is any
cat /run/systemd/shutdown/scheduled

# View scheduled shutdown in human-readable time format
awk -F= '/^USEC=/ { print $2 }' /run/systemd/shutdown/scheduled | awk '{ print strftime("%Y-%m-%d %H:%M:%S", $1 / 1000000) }'

Method 3: Using systemd Timer (Modern Systems)

For systems using systemd, you can create a timer:

Create a service file:

sudo nano /etc/systemd/system/restart.service

Add the following content:

[Unit]
Description=System Restart Service

[Service]
Type=oneshot
ExecStart=/sbin/shutdown -r now

[Install]
WantedBy=multi-user.target

Create a timer file:

sudo nano /etc/systemd/system/restart.timer

Add the following content for a daily 3:00 AM restart:

[Unit]
Description=Daily System Restart Timer

[Timer]
OnCalendar=*-*-* 03:00:00
Persistent=true

[Install]
WantedBy=timers.target

Enable and start the timer:

sudo systemctl enable restart.timer
sudo systemctl start restart.timer

Checking Your Scheduled Restarts

For Cron Jobs

sudo crontab -l

For Systemd Timers

systemctl list-timers

Additional Notes

Always test restart schedules during non-critical hours
Consider setting up monitoring to verify restarts occur as expected
For production systems, implement proper service recovery mechanisms
For shutdown without restart, replace -r with -h in shutdown commands for example

# Restart at a specific time today
sudo shutdown -r 23:00

# Shutdown at a specific time today (no restart)
sudo shutdown -h 23:00