This is an original planning guide. It is not a vendor manual, an official standard, or legal advice. Example addresses use documentation ranges. Review every command before you paste it.
What this hour is for
Cron is a line in a user's crontab. A systemd timer is a unit with an OnCalendar expression and a service that runs the command. The timer generator and the OnCalendar tester draft and explain text. They do not install a unit and they do not edit a crontab.
Pick one scheduler for the job. Two copies will run the job twice. A timer can persist a missed run after boot. That is a choice you write down, not a surprise. The user is not root unless the ticket says why.
Do not hide the job. Day-of-week fields need a person to read them. 192.0.2.10/24 and example.com are documentation. They stay in the note.
The change you can finish
Apply nothing while you are writing the note. When the lab window opens, it is one change on the host named in the ticket. Read the draft, then the host, then decide.
Rollback is the file, the package version, or the snapshot you saved first. You do not invent a rollback after the only copy is gone.
- Name the job and the user.
- Write the schedule in a sentence.
- Draft either a cron line or a timer, not both.
- Read the OnCalendar sentence if you chose a timer.
- Do not install either during the reading.
- Stop.
Mistakes that outlive the command
Cron vs systemd Timers goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- Both cron and a timer left enabled.
- A missed-run setting you did not choose.
- Root used without a reason.
- The units installed during the reading.
- A schedule you cannot say.
Decisions to write down
One decision for Cron vs systemd Timers: One scheduler. The user is named. Persistent is yes or no on purpose. Nothing was installed yet. And the sentence matches the clock.
Checks before you call it done
Confirm this before you call the change done: The job is named. One scheduler is chosen. The other is absent. Nothing was installed. And a second person can read the schedule. If one of those fails, stop.
| Question | Cron | systemd timer |
|---|---|---|
| Where it lives | A user's crontab | A timer unit and a service |
| A missed hour | It is skipped | Persistent can run it later, if you set that |
| This page | Does not install it | Does not install it |
# One scheduler.
# Do not enable cron and a timer for the same job.
# Read day-of-week fields.Before you leave the host
Cron vs systemd Timers ends when the hostname in the prompt matches the hostname in the ticket. If it does not, you are on the wrong host. Stop. A command that succeeded on the wrong host is not progress.
The draft stays a draft until a person has read the names in it. A generator does not log into the host and does not know which disk is empty. You delete a line that names a host, a path, or an account you did not write down.
192.0.2.10/24, gateway 192.0.2.1, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 are documentation. example.com is a documentation name. They belong in the note. They are not values you leave on a host because a draft included them.
prompt-for-this is a reminder that a secret is missing. It is not a password, a key, or a token you save in the ticket or in git. The real secret stays in the password store.
One change is the window. If two things move and the result is wrong, you will not know which one did it. The next change waits for its own page.
If the same step fails twice, stop for the day. The failure is the result. Adding a forum command beside a half-applied change produces a host nobody can rebuild. Restore the copy you took first.
A second person reads the hostname and the change aloud. If they cannot find them in the ticket, the note is not done. Silence is not agreement. Then leave the host alone.
This page is a planning guide. It is not a vendor manual, not an official standard, and not permission to touch a host you do not administer. You do not disable a firewall, AppArmor, or SELinux to make a check pass.
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