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Comment by amelius | Hacker News Reader

I make backups using cron, and recently I've been wondering what happens if the backup (hypothetically) takes longer than the interval between cron jobs. Will it start the new job while the old one is still running? Will unrelated cron jobs be blocked? And how is that in Mcron?

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Yes. If you're worried about this you can take a look at `flock`. e.g.

    flock -xn /path/to/lock -c /path/to/command

Yes - I believe it will start the new job while the old one is running - your backup script should write a PID file to ensure it isn't already running.

Systemd solves this at least, but I do like cron better.

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