# Timeshift

<p class="callout danger"><strong>IMPORTANT:</strong> Timeshift is <strong>not a backup tool!</strong> It only creates <em>local snapshots</em> of the system to roll back changes to the system. Do not rely on this mechanism to keep your data safe! Timeshift deletes the oldest snapshot when a new one is created and the maximum number of snapshots is reached. Furthermore, if the underlying file system is corrupted, the snapshots will be, too! Use a proper backup tool to keep your data safe on external data storage!</p>

Timeshift helps create incremental snapshots of the file system at regular intervals, which can then be restored at a later date to undo all changes to the system.

It supports `rsync` snapshots for all filesystems, and uses the built-in snapshot features for Btrfs drives configured to use the `@` and `@home` subvolume layout for *root* and *home* directories respectively. 

## Installation

Timeshift is available from the Arch repos. It uses cron to make regularly scheduled backups. Install Timeshift with a cron daemon, e.g. `cronie`:

~~~bash
pacman -S timeshift cronie
~~~

Start and enable the cron scheduler for Timeshift to take regular snapshots:

~~~bash
sudo systemctl enable --now cronie
~~~

Finally, start Timeshift and complete the first time setup.

## Automatic snapshots on system changes

In addition to Timeshift's periodic spanshots, `timeshift-autosnap` provides a `pacman` hook to create a manual snapshot every time packages are installed, upgraded or removed.

Install `timeshift-autosnap` from the AUR:

~~~bash
yay -S timeshift-autosnap
~~~

By default `timeshift-autosnap` only keeps 3 snapshots. To change this, edit `/etc/timeshift-autosnap.conf` and either set `deleteSnapshots` to `false` to never delete any snapshots or increase the number of `maxSnapshots`:

~~~
skipAutosnap=false
deleteSnapshots=true
maxSnapshots=7
updateGrub=true
snapshotDescription={timeshift-autosnap} {created before upgrade}
~~~

### Prevent excessive snapshotting when using `yay`

By default, when installing or updating multiple packages from the AUR, `yay` first builds a package and immediately calls `pacman` to install it, before building and installing the next one on its list. This also means that the `timeshift-autosnap` hook is triggered **for each individual AUR package** built by `yay`, **including dependencies also installed from the AUR.**

This can have undesireable side-effects:
* `yay` will cause `timeshift-autosnap` to reach the `maxSnapshots` limit very quickly when installing multiple packages from the AUR, leaving you with snapshots with little to no meaningful changes between them
* if `deleteSnapshots` is set to `false` the amount of snapshots might quickly exhaust the usable space on the drive

To prevent this it is recommended to configure `yay` to:
1. not remove make dependencies after successfully built packages are installed
1. build all AUR packages first, install them all later
1. install AUR packages together with regular repo packages

By calling `yay` with the `--save` parameter, any options passed to it will be saved in a configuration file, e.g.:

~~~bash
yay --noremovemake --batchinstall --combinedupgrade --save  
~~~

Next time you use `yay` to install, upgrade or remove packages it will read the generated config file at `~/.config/yay/config.json` and apply the options automatically without having to specify them during use.