Why can my cron job not find a specific command?

Question

I am using duplicity to create nightly backups of my server over FTP. I wrote a script that does both a local and remote backup and logs the output results. When I run this script as the root user, it executes just fine. However when I set it as a cron job and run it, the script executes but the ftp portion fails. Shortly after I get an error message saying "ncftpls - command not found, please install ncftp 3.1.9 or later" but it is installed! Is there some reason that cron job would not be able to find a command that exists on the machine? Does it have it's own PATH or something like that?

Any help is greatly appreciated,

Mike

Answer 1

Are you using absolute paths? Cron jobs won't open an interactive shell, so bash init scripts (bashrc, bash_profile, etc.) that usually set the PATH may not be run--and if they are, they'll be using root's, not yours. If you're unsure about where the command is, you can use which <command> to find out the absolute path.

When dealing with cron scripts, the general rule of thumb is, you either (a) want to set the PATH or (b) use absolute paths.

Good luck!

Answer 2

You should either give the full path to the command you want to run or you should define PATH in the cron job.

Example of running the foobar command without giving a path:

PATH=/sbin:/bin:/usr/sbin:/usr/bin
01 * * * * root foobar

With a path:

01 * * * * root /usr/bin/foobar

You can also specify things like which shell to run the jobs in by setting SHELL like: SHELL=/bin/bash for bash. See man 5 crontab for some more examples.