Override path like in zfs-auto-snapshot.cron.frequent

[proudier]

Using the installation method described in README on a fresh CentOS 8 install will result in the {hourly,daily,weekly,monthly} snapshots not being created while the 'frequent' ones are.

In the system log, one can read:

Dec 29 13:01:01 obfuscated CROND[6339]: (root) CMDOUT (/etc/cron.hourly/zfs-auto-snapshot:)
Dec 29 13:01:01 obfuscated CROND[6339]: (root) CMDOUT ()
Dec 29 13:01:01 obfuscated CROND[6339]: (root) CMDOUT (which: no zfs-auto-snapshot in (/sbin:/bin:/usr/sbin:/usr/bin))

By default, the script is installed under /usr/local/bin, which is not in the PATH when cron runs.
This PR add a PATH declaration to the {hourly,daily,weekly,monthly} cron files, similar to the frequent one.

[ahesford]

This is not portable. Not all cron implementations support a PATH declaration in crontab pieces. One affected implementation is dcron.

[antoinetran]

Hi, I reproduce the same issue and have the same conclusion as this pull request! Can we merge that?

Also about the non portable remark (@ahesford ) concerning /etc/cron.d/zfs-auto-snapshot (which is not part of this pull request BTW), one can just do

PATH="/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin"

*/15 * * * * root which zfs-auto-snapshot > /dev/null || exit 0 ; zfs-auto-snapshot --quiet --syslog --label=frequent --keep=4 //

=>

*/15 * * * * root export PATH="/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin" && which zfs-auto-snapshot > /dev/null || exit 0 ; zfs-auto-snapshot --quiet --syslog --label=frequent --keep=4 //

Maybe @proudier can you add that to your PR?