ZFS Prune Snapshots
===================

Remove snapshots from one or more zpools that match given criteria

Examples
--------

Remove snapshots older than a week across all zpools

    zfs-prune-snapshots 1w

Same as above, but with increased verbosity and without
actually deleting any snapshots (dry-run)

    zfs-prune-snapshots -vn 1w

Remove snapshots older than 3 weeks on tank1 and tank2/backup.
Note that this script will recurse through *all* of tank1 and
*all* datasets below tank2/backup

    zfs-prune-snapshots 3w tank1 tank2/backup

Remove snapshots older than a month on the zones pool that start
with the string "autosnap_"

    zfs-prune-snapshots -p 'autosnap_' 1M zones

Remove snapshots older than two months on the tank pool that end
with the string "_frequent"

    zfs-prune-snapshots -s '_frequent' 2M tank

Remove snapshots older than a month on the zones pool that do not
start with the string "autosnap_"

    zfs-prune-snapshots -i -p 'autosnap_' 1M zones

Timespec
--------

The first argument denotes how old a snapshot must be for it to
be considered for deletion - possible specifiers are

- `s` seconds
- `m` minutes
- `h` hours
- `d` days
- `w` weeks
- `M` months
- `y` years

Usage
-----

    usage: zfs-prune-snapshots [-hnliqRvV] [-p <prefix>] [-s <suffix>] <time> [[dataset1] ...]

    remove snapshots from one or more zpools that match given criteria

    examples
        # zfs-prune-snapshots 1w
        remove snapshots older than a week across all zpools

        # zfs-prune-snapshots -vn 1w
        same as above, but with increased verbosity and without
        actually deleting any snapshots (dry-run)

        # zfs-prune-snapshots 3w tank1 tank2/backup
        remove snapshots older than 3 weeks on tank1 and tank2/backup.
        note that this script will recurse through *all* of tank1 and
        *all* datasets below tank2/backup

        # zfs-prune-snapshots -p 'autosnap_' 1M zones
        remove snapshots older than a month on the zones pool that start
        with the string "autosnap_"

        # zfs-prune-snapshots -s '_frequent' 2M tank
        remove snapshots older than two months on the tank pool that end
        with the string "_frequent"

        # zfs-prune-snapshots -i -p 'autosnap_' 1M zones
        remove snapshots older than a month on the zones pool that do not
        start with the string "autosnap_"

    timespec
        the first argument denotes how old a snapshot must be for it to
        be considered for deletion - possible specifiers are

            s seconds
            m minutes
            h hours
            d days
            w weeks
            M months
            y years

    options
        -h             print this message and exit
        -n             dry-run, don't actually delete snapshots
        -l             list only mode, just list matching snapshots names
                       without deleting (like dry-run mode with machine-parseable output)
        -p <prefix>    snapshot prefix string to match
        -s <suffix>    snapshot suffix string to match
        -i             invert matching of prefix and suffix
        -q             quiet, do not printout removed snapshots
        -R             recursively delete, pass '-R' directly to 'zfs destroy'
        -v             increase verbosity
        -V             print the version number and exit

Development Notes
-----------------

### Style

[shellcheck](https://www.shellcheck.net/) is used to check bash style.  Use
`make check` to run the style checker:

    $ make check
    awk 'length($0) > 80 { exit(1); }' zfs-prune-snapshots
    shellcheck zfs-prune-snapshots

Bash style guide: https://www.daveeddy.com/bash/

### Manpage

Use `make man` to regenerate the manpage:

    $ make man
    md2man-roff man/zfs-prune-snapshots.md > man/zfs-prune-snapshots.1
    $ ./man/zfs-prune-snapshots.1
    <man page opens>

Manpages are generated with [md2man](https://github.com/sunaku/md2man) which
requires `ruby-devel` to be installed.  Once `ruby` is installed, `md2man` can
be installed locally with:

    $ gem install --user-install md2man

License
-------

MIT License