Quick answer
Open your user's crontab, add the line, save and exit. There is nothing to restart: cron picks up the change automatically.
crontab -e# m h dom mon dow command
*/5 * * * * /home/deploy/scripts/sync.sh >> /home/deploy/logs/sync.log 2>&1Tip
Not sure your expression means what you think? Paste it into the cron expression generator to see it in plain English with the next run times, or build one by picking minutes, hours and days.
How the five cron fields work
Each crontab line has five time fields followed by the command: minute (0–59), hour (0–23), day of month (1–31), month (1–12) and day of week (0–7, where both 0 and 7 are Sunday). An asterisk means "every value". A slash sets a step, so */5 in the minute field means every fifth minute starting from 0. A comma lists values (0,30), and a hyphen gives a range (9-17).
Steps are aligned to the clock, not to when you saved the crontab. */5 fires at minutes 0, 5, 10 … 55 of every hour. If you want an offset, for example to avoid every job on the server starting at the same moment, use a range with a step: 2-59/5 runs at :02, :07, :12 and so on. Note that */7 does not run every seven minutes across hour boundaries; it runs at 0, 7 … 56 and then again at 0, a gap of four minutes.
Note
When both day of month and day of week are restricted (neither is *), standard cron runs the job when either one matches, not both. 0 9 1 * 1 runs on the 1st of the month and on every Monday.
Common cron schedules
Copy the expression and put your command after it. Many cron implementations also accept the shortcuts @hourly, @daily, @weekly, @monthly and @reboot.
Read each expression from left to right: minute, hour, day of month, month, day of week. Restricting the hour and weekday fields is how you confine a frequent job to working hours, as in the business-hours example below, which runs 108 times a weekday and never at weekends. If you need an interval that does not divide evenly into 60, such as every 7 or 45 minutes, cron cannot express it exactly; a systemd timer with OnUnitActiveSec= can.
* * * * * every minute
*/5 * * * * every 5 minutes
*/10 * * * * every 10 minutes
*/15 * * * * every 15 minutes
*/30 * * * * every 30 minutes (same as 0,30 * * * *)
0 * * * * every hour, on the hour
0 */2 * * * every 2 hours
0 0 * * * every day at midnight
30 9 * * * every day at 09:30
0 9 * * 1-5 weekdays (Mon-Fri) at 09:00
*/5 9-17 * * 1-5 every 5 minutes, 09:00-17:55, weekdays
0 0 * * 0 every Sunday at midnight
0 0 1 * * first day of every month at midnight
0 3 * * 6 every Saturday at 03:00
@reboot once at system startuptimedatectl or date).Managing your crontab
Every user has a personal crontab, edited with crontab -e, which opens it in your $EDITOR and validates the syntax on save. crontab -l prints it, which is also an easy backup: crontab -l > crontab.bak. Jobs run as the user who owns the crontab, so put root-only tasks in root's crontab with sudo crontab -e rather than calling sudo inside a job.
System-wide jobs live in /etc/crontab and files under /etc/cron.d/. Those use a sixth field, the user name, between the schedule and the command.
crontab -l # list
crontab -l > crontab.bak # back up
crontab -e # edit
sudo crontab -u www-data -l # another user's crontab# /etc/cron.d/cleanup (note the user field)
*/5 * * * * root /usr/local/bin/cleanup.shWarning
crontab -r deletes your entire crontab immediately, with no confirmation on most systems, and the r key sits right next to e. Keep a backup from crontab -l.
Environment and PATH pitfalls
Cron does not run your login shell. Jobs start with /bin/sh, a minimal PATH (often just /usr/bin:/bin), and none of the variables from .bashrc, .profile, nvm, pyenv or your virtualenv. A script that works perfectly in your terminal can fail in cron with "command not found". The fixes:
- Use absolute paths for every program and file:
/usr/bin/python3,/usr/local/bin/node,/home/deploy/app/.venv/bin/python. Find them withwhich. - Or set PATH (and SHELL if you need bash) at the top of the crontab.
cdinto the project directory first, because the working directory is your home directory, not the script's folder.- Escape percent signs as
\%. In a crontab line an unescaped%ends the command and turns the rest into standard input, which breaksdate +%F. - Load secrets explicitly, for example by sourcing an env file inside the script, since nothing from your interactive session is available.
SHELL=/bin/bash
PATH=/usr/local/bin:/usr/bin:/bin
MAILTO=""
*/5 * * * * cd /home/deploy/app && .venv/bin/python manage.py sync >> logs/sync.log 2>&1
0 2 * * * /usr/bin/tar czf /backups/site-$(date +\%F).tgz /var/www/siteLogging output and debugging
By default cron tries to email a job's output to the crontab owner, which on most servers goes nowhere. Redirect both standard output and errors to a log file with >> file 2>&1 so you can see what happened. To confirm that cron started the job at all, check the system log.
If a job runs every 5 minutes but sometimes takes longer than 5 minutes, runs will overlap. Wrap it in flock -n so a new run is skipped while the previous one still holds the lock.
*/5 * * * * /home/deploy/sync.sh >> /home/deploy/logs/sync.log 2>&1
# Did cron start it?
grep CRON /var/log/syslog # Debian / Ubuntu
journalctl -u cron --since "1 hour ago" # Debian / Ubuntu with systemd
journalctl -u crond --since today # RHEL / Fedora / Rocky
# Prevent overlapping runs
*/5 * * * * /usr/bin/flock -n /tmp/sync.lock /home/deploy/sync.sh >> /home/deploy/logs/sync.log 2>&1Alternative: systemd timers
On modern Linux servers, systemd timers are a robust alternative to cron. They log to the journal automatically, will not start a second copy while the service is still running, can catch up on runs missed while the machine was off (Persistent=true), and can add random delay to spread load. The cost is two small files instead of one line. OnCalendar=*:0/5 means every 5 minutes, and systemd-analyze calendar checks an expression before you use it.
# /etc/systemd/system/sync.service
[Unit]
Description=Sync job
[Service]
Type=oneshot
User=deploy
ExecStart=/home/deploy/sync.sh# /etc/systemd/system/sync.timer
[Unit]
Description=Run sync every 5 minutes
[Timer]
OnCalendar=*:0/5
Persistent=true
[Install]
WantedBy=timers.targetsystemd-analyze calendar "*:0/5"
sudo systemctl daemon-reload
sudo systemctl enable --now sync.timer
systemctl list-timers
journalctl -u sync.serviceAlternative: GitHub Actions schedule
GitHub Actions workflows can run on a cron schedule with the same five-field syntax, which is handy for jobs that do not need a server. There are important differences from system cron: schedules always use UTC, the shortest interval GitHub supports is once every 5 minutes, scheduled runs use the workflow file on the default branch, and runs can start late or occasionally be skipped when GitHub is under heavy load, especially at the top of the hour. In public repositories, scheduled workflows are disabled automatically after 60 days without repository activity. Add workflow_dispatch so you can also trigger the job manually.
# .github/workflows/sync.yml
name: Sync every 5 minutes
on:
schedule:
- cron: "*/5 * * * *" # UTC
workflow_dispatch:
jobs:
sync:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- run: ./scripts/sync.shTip
Because GitHub schedules can slip by several minutes, use an off-peak minute such as 7,37 * * * * for jobs that need to run reliably, and keep time-critical work on a server cron or systemd timer.
Cron every 5 minutes: FAQ
Quick answers to common questions
What is the cron expression for every 5 minutes?
*/5 * * * *. It runs at minutes 0, 5, 10 and so on through 55 of every hour, every day. Check any expression in the cron expression generator.
Why is my cron job not running?
Most often it runs but fails because of cron's minimal environment: use absolute paths, set PATH in the crontab, cd into the right directory, escape % signs and redirect output to a log file to see the error.
Can cron run a job every 5 seconds?
No. Cron's smallest unit is one minute. For sub-minute intervals use a systemd timer with OnUnitActiveSec=5s, a loop with sleep inside a long-running service, or a job scheduler in your application.
What time zone does cron use?
System cron uses the server's local time zone, so check it with timedatectl. GitHub Actions schedules always use UTC.
What is the difference between */5 and 0/5 in cron?
In standard Linux cron (Vixie cron, cronie) both mean every fifth minute starting at 0. */5 is the portable form; Quartz and some other schedulers use a six- or seven-field syntax where 0/5 is the norm.