apt-snapshot

apt-snapshot manages constantly rolling snapshots of root filesystem allowing rollback to a previous state.

Installation

• Copy apt-snapshot to /usr/local/sbin : cp apt-snapshot /usr/local/sbin
• Make the script executable : chmod +x /usr/local/sbin/apt-snapshot
• Copy apt-snapshot.default to /etc/default/apt-snapshot cp apt-snapshot.default /etc/default/apt-snapshot
• Customize /etc/default/apt-snapshot (see examples below).
• Select the right method to create periodic snapshots with apt-snapshot :

0. At each apt update invokation, interactive or batch (via unattended-upgrades) : Copy the provided apt-snapshot.conf to /etc/apt/apt.conf.d/ cp apt-snapshot.conf /etc/apt/apt.conf.d/90apt-snapshot

1. Every hour / day / week / month / year (hourly and yearly should be avoided you're warned) : Link /usr/local/sbin/apt-snapshot to /etc/cron.[daily|weekly|monthly]/apt-snapshot. Example for daily snapshot : ln -s /usr/local/sbin/apt-snapshot /etc/cron.daily/apt-snapshot

If you want the cronjob to report only errors, create a line in a standard cron.d/apt-snapshot file containing for example weekly runs :

@weekly root apt-snapshot >/dev/null

Usage

apt-snapshot keeps N rolling snapshots configured in /etc/default/apt-snapshot file. In case something went wrong during an update, rollback to a previous snapshot with :

lvconvert --merge /dev/<VG>/<LV>_snapNNNN and reboot.

Default file variables examples

ORIGIN_VG

Volume Group name : the VG containing the Logical Volume we want to snapshot before upgrades. On many default system installations, this is the host name or something similar. It can be found via the following commands : vgscan or vgs. If there's only one VG then you're done, otherwise, you should know what you did !

ORIGIN_LV

Logical Volume we want to snapshot before upgrades. It can be found via the following commands : lvs or lvscan. If there's only one LV then you're done again, otherwise, you should know what you did and find the right LV name to use.

PERCENT_SIZE

The size of the snapshot that we will create in % of the original LV size. If the original LV is 10GB and PERCENT_SIZE="50%" then your snapshot will size 5GB and will be able to track 5GB of changes from the original LV data.

SNAP_DEVICES_COUNT

Non mandatory : will default to 1 if commented. The number of devices the VG spans on. For example, if the LV is in a VG that can span to 3 disks in raid0 or raid1, then it should be set to 3.

SNAP_DEVICES

Non mandatory : will default to the only one PV (Physical Volume) the list of PV (Physical Volumes) devices the VG spans on separated by spaces. For example :

SNAP_DEVICES="/dev/sda2 /dev/sdb2"

SNAP_HISTORY_KEEP

The number of snapshots to keep. Before each new snapshot creation, the script will ensure that the total number of snapshot will not exceed that number by removing the older one in a roll over mode.