Amanda LVM-snapshot Plugin
==========================

This plugin provides support for LVM snapshots in Amanda dumps.  It interfaces
with Amanda through the [Script API][1].

Install
-------

Sorry, there's no Makefile yet. Simply copy the amlvm-snapshot.pl script into
Amanda's application directory.

For example:

    cp amlvm-snapshot.pl /usr/libexec/amanda/application/amlvm-snapshot

You may need to edit the location of Amanda's Perl libraries in the script
itself, the following line.

    use lib '/usr/local/share/perl/5.8.4';

Configure Amanda
----------------

Somewhere in your Amanda config you must define a `script-tool` that loads the
plugin. You can simply include the provided `lvm-snapshot.conf` file if you like.

    cp lvm-snapshot.conf /etc/amanda/DailySet1/lvm-snapshot.conf
    echo 'includefile "lvm-snapshot.conf"' >> /etc/amanda/DailySet1/amanda.conf

Once you have the `lvm-snapshot` `script-tool` defined, you can include it in
a `dumptype` definition. Note, however, that your dumptype _must use an
application-tool program_: Only application-tool programs can handle the
alternate mount point—of the snapshot device—that the script defines.

    define dumptype lvm-comp-amgtar {
      comment "LVM snapshot dumped with amgtar"
      global
      program "APPLICATION"
      application "app_amgtar"
      script "lvm-snapshot"
      compress client fast
      index
    }

To allow amanda to dump more than one lvm-snapshot in parallel,
lvm-snapshot.conf has to have something like:

      property "SNAPSHOT-SIZE" "250"

(the unit is PEs, for LVM PE Size 4,00 MiB it results in 1G snapshot-size)

otherwise the first snapshot uses up all extents and the second snapshot fails.

Configure Permissions
---------------------

This plugin requires elevated permissions in order to create and remove LVM
devices. There are two ways to provide access: setting setuid on the plugin
script itself, or by configuring `sudo` to allow execution of the LVM
programs.

### setuid

NOTE: I'm currently having trouble getting this to work right, as Amanda's
Perl libraries don't seem to play nice with setuid scripts.

For setuid, simply configure the ownership and mode on `amlvm-snapshot`. In
this example, `disk` is the group that Amanda runs under.

    chown root:disk /usr/libexec/amanda/application/amlvm-snapshot
    chmod 4750 /usr/libexec/amanda/application/amlvm-snapshot

This will require that you have a version of Perl installed that was compiled
with `ENABLE_SUIDPERL`.

### sudo

For sudo, add the following to the `/etc/sudoers` file where "amandabackup" is
the name of your Amanda user.

    amandabackup    ALL=(ALL) NOPASSWD: /sbin/lvcreate, /sbin/lvdisplay, /sbin/lvremove, /sbin/vgdisplay, /bin/readlink, /bin/mount, /bin/umount, /sbin/blkid

The commands listed are those used by `amlvm-snapshot` to interact with the
LVM volumes.

Remember to enable the `SUDO` property. This is already included in the
example `lvm-snapshot.conf` file.

    define script-tool lvm-snapshot {
      # ...
      property "SUDO" "1"
    }

Enjoy,
Daniel

[1]: http://wiki.zmanda.com/index.php/Script_API