'\" t .TH SNAP-PAC 8 2021-01-29 SNAP-PAC .SH NAME snap-pac \- Pacman hooks that use snapper to create pre/post btrfs snapshots like openSUSE's YaST .SH DESCRIPTION This is a set of \fIpacman\fR hooks and script that causes \fIsnapper\fR to automatically take a pre and post snapshot before and after pacman transactions, similar to how YaST does with OpenSuse. This provides a simple way to undo changes to a system after a pacman transaction. Because these are pacman hooks, it doesn't matter how you call pacman—whether directly, through an AUR helper, or using an alias—snapper will create the snapshots when pacman installs, upgrades, or removes a package. The pacman command used is logged in the snapper description for the snapshots. Additionally the snapshot numbers are output to the screen and to the pacman log for each snapper configuration during the pacman transaction, so that the user can easily find which changes he or she may want to revert. To undo changes from a pacman transaction, use \fIsnapper undochange\fR. See \fBsnapper\fR(8) and \fBEXAMPLES\fR. If you have severe breakage—like snapper is gone for some reason and you can't get it back—you'll have to resort to more extreme methods, such as taking a snapshot of the pre snapshot and making it the default subvolume or mounting it as \fI/\fR. Most likely you'll need to use a live USB to get into a chroot environment to do any of these things. Snapper has a snapper rollback feature, but your setup has to be properly configured to use it. The exact procedure depends on your specific setup. Be careful. .SH CONFIGURATION Configuration is done via configuration files. The defaults of the following should be suitable for most users, so you may not need to do any configuration at all. Follow the pattern of bash shell variables (VAR=setting) in each configuration file below. Comments can be added by adding \fI#\fR before the comment. Example configuration files are located at \fI/etc/snap-pac.conf.example\fR and \fI/etc/snap-pac/root.conf.example\fR. The following settings can be changed in the main snap-pac configuration file \fI/etc/snap-pac.conf\fR: \fBABORT_ON_FAIL=\fR\fB\fIyes\fR\fR\fB or \fR\fB\fIno\fR\fR .RS 4 When set to "yes" this causes pacman to abort a transaction if the snap-pac pre hook fails. This prevents an upgrade/installation/removal from occurring if a pre snapshot cannot be performed. Default is "no". .RE \fBDESC_LIMIT=\fR\fB\fIinteger\fR\fR .RS 4 Number of characters to limit length of descriptions used for snapper. Default is "72". .RE The following are possible settings used on each specific snapper configuration you have. To use them, first create the folder \fI/etc/snap-pac\fR if it does not already exist. Then create a file for the snapper configuration file you want these settings to apply to. For example, for the snapper configuration named \fIroot\fR, create the file \fI/etc/snap-pac/root.conf\fR. \fIsnap-pac\fR requires and expects configuration files to end in \fI.conf\fR. \fBSNAPSHOT=\fR\fB\fIyes\fR\fR\fB or \fR\fB\fIno\fR\fR .RS 4 Perform pacman pre/post snapshots for this configuration. In other words, if you want snapper to run before and after a pacman transaction, set this to "yes". Default is "no", except for the root configuration which is "yes". .RE .BR CLEANUP_ALGORITHM .RS 4 \fBsnapper\fR algorithm used in cleaning up the pacman pre/post snapshots. See \fBsnapper\fR(8) for a list of valid options. Default is "number". .RE \fBPRE_DESCRIPTION=\fR\fB\fIstring\fR\fR .RS 4 \fBsnapper\fR description used for the pacman pre snapshot. Default is the parent program, usually \fBpacman\fR, that called the snapshot script. .RE \fBPOST_DESCRIPTION=\fR\fB\fIstring\fR\fR .RS 4 \fBsnapper\fR description used for the pacman post snapshot. Default is the list of packages that were installed/upgraded/removed during the transaction. .RE .SH ENVIRONMENT VARIABLES To temporarily prevent snapshots from being performed for a single pacman command, set the environment variable \fISNAP_PAC_SKIP\fR. For example: .EX $ sudo SNAP_PAC_SKIP=y pacman -Syu .EE .SH EXAMPLES Here is an example of how the snapshots are created and how to rollback and pacman transaction. Here the \fBnano\fR package is installed: .EX # pacman -S nano resolving dependencies... looking for conflicting packages... Packages (1) nano-2.5.3-1 Total Installed Size: 2.14 MiB :: Proceed with installation? [Y/n] Y (1/1) checking keys in keyring [######################################] 100% (1/1) checking package integrity [######################################] 100% (1/1) loading package files [######################################] 100% (1/1) checking for file conflicts [######################################] 100% (1/1) checking available disk space [######################################] 100% :: Running pre-transaction hooks... (1/1) Performing snapper pre snapshots for the following configurations... => root: 1033 :: Processing package changes... (1/1) installing nano [######################################] 100% :: Running post-transaction hooks... (1/1) Performing snapper post snapshots for the following configurations... => root: 1034 .EE The snapper snapshot number is given for each snapper configuration that is used. This is also logged in pacman's log. Here are the snapshots created before and after the pacman transaction: .EX # snapper -c root list -t pre-post | tail -n 1 1033 | 1034 | Fri 22 Apr 2016 01:54:13 PM CDT | Fri 22 Apr 2016 01:54:14 PM CDT | pacman -S nano | .EE Here is what changed during the transaction: .EX # snapper -c root status 1033..1034 +..... /etc/nanorc c..... /etc/snapper/.snap-pac-pre +..... /usr/bin/nano +..... /usr/bin/rnano +..... /usr/share/doc/nano +..... /usr/share/doc/nano/faq.html +..... /usr/share/doc/nano/fr +..... /usr/share/doc/nano/fr/nano.1.html +..... /usr/share/doc/nano/fr/nanorc.5.html +..... /usr/share/doc/nano/fr/rnano.1.html .EE The above output is truncated, but it continues. See the \fBsnapper\fR(8) to for what each symbol means. You can also do \fBsnapper diff\fR in the same way. Then, to undo the \fBpacman\fR transaction: .EX # snapper -c root undochange 1033..1034 create:0 modify:3 delete:100 .EE Now nano is no longer installed, along with all the files it changed: .EX $ pacman -Qi nano error: package 'nano' was not found .EE .SH TROUBLESHOOTING .SS snap-pac is only taking snapshots of the root configuration. That's the default behavior. See \fBCONFIGURATION\fR. .SS No snapshots are being taken when I run pacman. No snapper configurations are set up for snap-pac's pacman hooks. By default snap-pac will take snapshots for the root configuration and any other configuration which has SNAPSHOT set to yes in its configuration file. See \fBCONFIGURATION\fR. .SS After restoring snapshot from snap-pac, the pacman database is locked. The pre/post snaphots are taken while pacman is running, so this is expected. Follow the instructions pacman gives you (e.g., removing the lock file). You can add the database lock file to a snapper filter so that snapper won't consider it when performing \fBsnapper diff\fR, \fBsnapper status\fR, \fBsnapper undochange\fR, etc. See the \fBFilters\fR section in \fBsnapper\fR(8) for more information. .SH FAQ .SS Does snap-pac backup non-btrfs /boot partitions? No, but you can add a hook that does it for you. It would be something like the following: .EX [Trigger] Operation = Upgrade Operation = Install Operation = Remove Type = Package Target = linux [Action] Description = Backing up /boot... When = PreTransaction Exec = /usr/bin/rsync -avzq --delete /boot /.bootbackup .EE .SS How do I link old kernel modules automatically when the kernel is upgraded? This behavior is no longer a part of this package. Use a pacman hook like the following: [Trigger] Operation = Upgrade Operation = Install Operation = Remove Type = Package Target = linux [Action] Description = Symlinking old kernel modules... When = PostTransaction Exec = /usr/bin/bash -c "find /usr/lib/modules -xtype l -delete; ln -sv /.snapshots/$(snapper -c root list | awk 'END{print $1}')/snapshot/usr/lib/modules/$(uname -r) /usr/lib/modules/" .SH HOMEPAGE https://github.com/wesbarnett/snap-pac .SH AUTHORS Wes Barnett .SH SEE ALSO .BR alpm-hooks (5), .BR snapper (8), .BR snapper-configs (5), .BR pacman (8)