143 lines
5.2 KiB
Markdown
143 lines
5.2 KiB
Markdown
# snap-pac
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This makes Arch Linux's pacman use
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[snapper](https://wiki.archlinux.org/index.php/Snapper) to automatically take a
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pre and post snapshot before and after pacman transactions using pacman's hooks
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feature, similar to how YaST does with OpenSuse. This provides a simple way to
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undo changes to a system after a pacman transaction.
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The snapshots are set up to use snapper's `number` algorithm. That is, snapper
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will periodically clean up snapshots tagged with `number` after reaching a set
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threshold in the snapper configuration file.
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**Note:** Snapshots are only taken of the subvolume corresponding with the
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`root` snapper config; other subvolumes are not included. You must modify the
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scripts to include other subvolumes. Additionally, you should create subvolumes
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of directories you do *not* want included in your snapshots (*e.g.*
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`/var/cache/pacman/pkg`).
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## Installation
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Install [the package from the
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AUR](https://aur.archlinux.org/packages/snap-pac/).
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After installation, the hooks are located at `/usr/share/libalpm/hooks`, and the
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scripts are located at `/usr/share/libalpm/hooks.bin/snap-pac`.
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## Configuration
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The configuration file is located at `/etc/snap-pac.conf`. There you can choose
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which snapper configurations of which to take snapshots, the descriptions used
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for the snapshots, and the snapper algorithm to use.
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## Usage
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### Taking snapshots
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**Use pacman—and AUR helpers—as normal and watch snapper do its thing.** No
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bash scripts for you to call. No bash aliases to setup.
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Because these are pacman hooks, it doesn't matter how you call pacman—whether
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directly, through an AUR helper, or using an alias—snapper will create the
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snapshots when pacman installs, upgrades, or removes a package. The
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pacman command used is logged in the snapper description for the
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snapshots.
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### Undoing a transaction
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To undo changes from a pacman transaction, use `snapper undochange`. See the
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snapper manpage and the following example.
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## Example
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Installing the `nano` package as normal:
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# pacman -S nano
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resolving dependencies...
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looking for conflicting packages...
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Packages (1) nano-2.5.3-1
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Total Installed Size: 2.14 MiB
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:: Proceed with installation? [Y/n] Y
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(1/1) checking keys in keyring [######################################] 100%
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(1/1) checking package integrity [######################################] 100%
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(1/1) loading package files [######################################] 100%
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(1/1) checking for file conflicts [######################################] 100%
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(1/1) checking available disk space [######################################] 100%
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:: Running pre-transaction hooks...
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(1/1) snapper pre snapshot
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:: Processing package changes...
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(1/1) installing nano [######################################] 100%
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:: Running post-transaction hooks...
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(1/2) snapper post snapshot
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(2/2) generate GRUB configuration file
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And here are the snapshots:
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# snapper -c root list -t pre-post | tail -n 1
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1033 | 1034 | Fri 22 Apr 2016 01:54:13 PM CDT | Fri 22 Apr 2016 01:54:14 PM CDT | pacman -S nano |
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What changed?
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# snapper -c root status 1033..1034
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+..... /etc/nanorc
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c..... /etc/snapper/.snap-pac-pre
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+..... /usr/bin/nano
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+..... /usr/bin/rnano
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+..... /usr/share/doc/nano
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+..... /usr/share/doc/nano/faq.html
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+..... /usr/share/doc/nano/fr
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+..... /usr/share/doc/nano/fr/nano.1.html
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+..... /usr/share/doc/nano/fr/nanorc.5.html
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+..... /usr/share/doc/nano/fr/rnano.1.html
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I truncated the above output, but it continues. See the manpage for snapper to
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see what each symbol means. You can also do `snapper diff` in the same
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way—I'll spare you that one.
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To undo the upgrade:
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# snapper -c root undochange 1033..1034
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create:0 modify:3 delete:100
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And `nano` is now gone, along with all the files it changed:
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$ pacman -Qi nano
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error: package 'nano' was not found
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## License
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snap-pac
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Copyright (C) 2016 James W. Barnett
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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## See also
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* [ArchWiki Btrfs article](https://wiki.archlinux.org/index.php/Btrfs)
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* [ArchWiki Snapper article](https://wiki.archlinux.org/index.php/Snapper)
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* [Btrfs homepage](https://wiki.archlinux.org/index.php/Btrfs)
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* [snapper homepage](http://snapper.io/)
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* `man alpm-hooks`
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* `man btrfs`
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* `man snapper`
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