├── LICENSE
├── README.md
└── screenshots
├── debian_part1.png
├── debian_part10.png
├── debian_part11.png
├── debian_part12.png
├── debian_part13.png
├── debian_part14.png
├── debian_part15.png
├── debian_part16.png
├── debian_part17.png
├── debian_part18.png
├── debian_part19.png
├── debian_part2.png
├── debian_part20.png
├── debian_part21.png
├── debian_part3.png
├── debian_part4.png
├── debian_part5.png
├── debian_part6.png
├── debian_part7.png
├── debian_part8.png
├── debian_part9.png
├── grub_menu_boot1.png
├── grub_menu_boot1_kernel.png
├── grub_snapshots1.png
└── grub_snapshots2.png
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623 | How to Apply These Terms to Your New Programs
624 |
625 | If you develop a new program, and you want it to be of the greatest
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627 | free software which everyone can redistribute and change under these terms.
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629 | To do so, attach the following notices to the program. It is safest
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649 |
650 | Also add information on how to contact you by electronic and paper mail.
651 |
652 | If the program does terminal interaction, make it output a short
653 | notice like this when it starts in an interactive mode:
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658 | under certain conditions; type `show c' for details.
659 |
660 | The hypothetical commands `show w' and `show c' should show the appropriate
661 | parts of the General Public License. Of course, your program's commands
662 | might be different; for a GUI interface, you would use an "about box".
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664 | You should also get your employer (if you work as a programmer) or school,
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667 | .
668 |
669 | The GNU General Public License does not permit incorporating your program
670 | into proprietary programs. If your program is a subroutine library, you
671 | may consider it more useful to permit linking proprietary applications with
672 | the library. If this is what you want to do, use the GNU Lesser General
673 | Public License instead of this License. But first, please read
674 | .
675 |
--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
1 | # Debian with Automated Snapper Rollbacks
2 |
3 | This is a short tutorial about setting up a Debian linux system with automated BTRFS snapshots of the system and easy rollback to previous auto-generated snapshots. The tutorial is inspired by the [SpiralLinux](https://github.com/SpiralLinux/SpiralLinux-project) distribution, which configures this automatically upon install.
4 |
5 | 
6 | 
7 |
8 | # Motivation
9 |
10 | At the time of writing, Debian by default will install using an `ext4` file system. This works fine for the kind of features that were envisioned for file systems at the time unixes were born, but in today's landscape, other file systems can offer many additional features that come very handy for desktop usage.
11 |
12 | Since the introduction of `ext`-type systems, there have been many advances in the field as implemented in systems such as ZFS or BTRFS, which bring functionalities like copy-on-write (COW), automatic snapshots achieved through the COW system, automated compression, encryption, among others.
13 |
14 | In particular, for desktop usage, one would typically want to have a way of rolling back some software update or going back to how the computer was a few days ago. This is now possible to do through automated snapshots (which thanks to the COW system, are instantaneous to generate and do not take much extra space), and is implemented automatically in other distributions such as OpenSuSe, but in Debian, it takes a few more manual steps to get it working.
15 |
16 | Thanks to software like [snapper](https://github.com/openSUSE/snapper), [grub-btrfs](https://github.com/Antynea/grub-btrfs) and [snapper-rollback](https://github.com/jrabinow/snapper-rollback), it's possible to have the same system in Debian in which:
17 |
18 | * Automated file system snapshots are generated every time `apt` or similar is executed.
19 | * Snapshots are also generated daily and the last N-selected days of snapshots kept at any given time.
20 | * The boot menu offers to boot into any of the available snapshots.
21 | * The system can be rolled back to a previous snapshot, and this can be done while booting from an older snapshot too.
22 |
23 | Note that this combination of `snapper` + `grub-btrfs` + `snapper-rollback` is not the only way of achieving such system - for example, [timeshift](https://github.com/linuxmint/timeshift) and [yabsnap](https://github.com/hirak99/yabsnap) can also be used with `grub-btrfs` instead of `snapper`, and similar alternatives exist for ZFS such as [ZFSBootMenu](https://github.com/zbm-dev/zfsbootmenu). This guide is **specifically for snapper** and BTRFS however.
24 |
25 | # Overview
26 |
27 | This guide outlines the necessary steps to configure the kind of system described above using the combination of `snapper` + `snapper-rollback` + `grub-btrfs`.
28 |
29 | * [A premier about BTRFS](https://github.com/david-cortes/snapper-in-debian-guide#a-premier-about-btrfs)
30 | * [Installing Debian with a BTRFS partition](https://github.com/david-cortes/snapper-in-debian-guide#installing-debian-with-a-btrfs-partition)
31 | * [Creating required BTRFS subvolumes](https://github.com/david-cortes/snapper-in-debian-guide#creating-required-btrfs-subvolumes)
32 | * [Installing and configuring software for snapshots and rollbacks](https://github.com/david-cortes/snapper-in-debian-guide#installing-and-configuring-software-for-snapshots-and-rollbacks)
33 | * [Performing a system rollback](https://github.com/david-cortes/snapper-in-debian-guide#performing-a-system-rollback)
34 | * [Caution: booting snapshots and kernels](https://github.com/david-cortes/snapper-in-debian-guide#caution-booting-snapshots-and-kernels)
35 | * [Snapshots for the `/home` subvolume](https://github.com/david-cortes/snapper-in-debian-guide#snapshots-for-the-home-subvolume)
36 |
37 | # A premier about BTRFS
38 |
39 | The BTRFS file system differs a bit from the paradigms that previous generations of file systems followed. One can read the [Wikipedia article about it](https://en.wikipedia.org/wiki/Btrfs) for more information. A few points for the purposes of this guide:
40 |
41 | * It uses the concept of _subvolumes_, which are similar to disk partitions. Multiple subvolumes can be generated inside a single BTRFS partition, and in many ways they work the same as partitions (e.g. one can delete/clone a subvolume without touching the rest of the system, have specific options for it like compression or no compression, make snapshots, etc.), but with the added benefit that subvolumes within the same volume do not introduce a space limit barrier, unlike hard partitions. Just like with partitions, these subvolumes can be referenced in the file `/etc/fstab` in order to mount them at the desired system paths with the desired options.
42 | * Internally, BTRFS can leverage compression algorithms like ZSTD or LZMA, which allow decreasing the space that files take on disk. In today's landscape, reading contents from a disk file is many orders of magnitude slower than doing operations with them on RAM, thus compression can make reading disk files faster, as reading and decompressing a smaller chunk of memory from RAM is oftentimes faster than reading the whole content from disk. This however will lead to misleading reporting of space taken.
43 | * It can use copy-on-write for handling file writes - meaning: it's possible to obtain a previous version of a file by unrolling the changes that were done to it, if these files are represented by incremental changes. And note that, if only changes are stored, having multiple versions of files available doesn't necessarily take as much space as if independent copies were stored. This is not free however as it requires extra RAM when doing disk operations, and for optimal performance, requires disk de-fragmentation like in older systems.
44 |
45 | In order to enable or disable options like compression in a BTRFS subvolume, one needs to modify their mount options in the file `/etc/fstab`. For example, upon install, debian might mount the root BTRFS volume with a line like this:
46 | ```
47 | UUID= / btrfs defaults,subvol=@rootfs 0 0
48 | ```
49 |
50 | Key there is the part where it says `defaults,subvol=@rootfs`. One can modify this chunk right there to enable further features - e.g.:
51 | ```
52 | UUID= / btrfs defaults,compress=zstd,autodefrag,subvol=@rootfs 0 0
53 | ```
54 |
55 | (Note: only 1 space or tab is required between chunks in the file, the rest are just for visual aid)
56 |
57 | A very good source of information about handling of BTRFS systems, options, commands, etc. is the [Arch wiki](https://wiki.archlinux.org/title/Btrfs).
58 |
59 | # Installing Debian with a BTRFS partition
60 |
61 | During installation of Debian, be sure to create a **single** partition of BTRFS type for your system **PLUS** a separate partition for `/boot`. The boot partition doesn't need to be BTRFS, and only requires a small size to work (1GB will suffice as of 2023). You'll probably want another partition for SWAP too.
62 |
63 | It's pretty straight-forward to do this with the installer, but here are some screenshots in case it's not clear. Note that you'll probably want to set up a larger SWAP partition than what's shown in the screenshots.
64 |
65 | **IMPORTANT:** these screenshots depict the process assuming the system is booting in legacy BIOS mode. For UEFI systems, you'll also need a `/boot/efi` entry (screenshots about it to come in the future).
66 |
67 | 
68 |
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70 |
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84 |
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94 |
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96 |
97 | 
98 |
99 | 
100 |
101 | 
102 |
103 | 
104 |
105 | 
106 |
107 | 
108 |
109 |
110 | Optionally, you might also want to enable encryption. Note that in such case, you'll probably want to put both the BTRFS partition and the SWAP partition under the same encrypted logical volume. The installer's UI is rather cumbersome for such configurations, but some google searches might help.
111 |
112 | See this longer step-by-step guide for more advanced configurations through the installer, including creating an encrypted volume for both the BTRFS and SWAP partitions together:
113 | https://unix.stackexchange.com/a/577765/342846
114 |
115 | # Creating required BTRFS subvolumes
116 |
117 | ## Prequesitive: install `sudo` and necessary software
118 |
119 | This guide uses `sudo` for the rest of the commands that it suggests. `sudo` should come by default in a debian install, but **if you added a root password in the installer**, your user will not be able to use `sudo` by default.
120 |
121 | Thus, as a first step, configure `sudo` for your user (**warning:** these instructions sketch an "unsafe" way of doing it - one can also use the `sudoers` user group):
122 |
123 | * Log in as the root user by issuing:
124 | ```shell
125 | su
126 | ```
127 | (then enter the root password)
128 | * Add a line to the file `/etc/sudoers` giving your user all the `sudo` permissions:
129 | ```shell
130 | printf " ALL=(ALL:ALL) ALL\n" >> /etc/sudoers
131 | ```
132 | (replace `` with the name of your linux user)
133 | * Exit from the `su` session:
134 | ```shell
135 | exit
136 | ```
137 | * Now you can use `sudo` with your user. Try the following in order to update the package cache:
138 | ```shell
139 | sudo apt-get update
140 | ```
141 | * If it doesn't succeed, you might manually need to modify the file `/etc/apt/sources.list` to _not_ use the debian installation CD/DVD and instead use an internet repository. It's highly recommended that you google about it if you aren't familiar with it, but as a quick note, the following will do:
142 | * Edit the file with your favorite text editor (note that it requires `sudo` permissions to overwrite the file):
143 | ```shell
144 | sudo nano /etc/apt/sources.list
145 | ```
146 | * Comment out any lines starting with `cdrom`, by putting a `#` character at the beginning of such lines.
147 | * Add a line with the debian main repository (for better results, replace "stable" with the name of the debian release - e.g. "bookworm", "trixie", "forky", etc.):
148 | ```
149 | deb http://deb.debian.org/debian/ stable main
150 | ```
151 | * Optionally, if you want non-Stallman-approved software, you can add additional parts of the repository there - make the line like this instead:
152 | ```
153 | deb http://deb.debian.org/debian/ stable main contrib non-free non-free-firmware
154 | ```
155 | * Save the file (Ctrl+O if you are using `nano` to edit it) and try the command again:
156 | ```shell
157 | sudo apt-get update
158 | ```
159 |
160 | Now that you've configured `sudo` and refreshed the repositories cache, you'll want to install a few key software packages for the rest of this guide:
161 | ```shell
162 | sudo apt-get install btrfs-progs python3-btrfsutil gawk inotify-tools make build-essential git
163 | ```
164 |
165 | _Note: for this section, you only need `btrfs-progs`, but for the following sections you'll also need the rest in order to install `grub-btrfs` and `snapper-rollback`._
166 |
167 | ## Required structure
168 |
169 | As a preliminary step, one can read through the [Arch wiki](https://wiki.archlinux.org/title/Snapper#Suggested_filesystem_layout) for a suggested layout and instructions for how to accomplish things with BTRFS and snapper.
170 |
171 | For the software that this guide uses, you might or might not follow the Arch wiki suggestions, but at the bare minimum, you'll need to create separate BTRFS subvolumes or separate partitions for these key system paths, and manually add them to your `/etc/fstab` file:
172 |
173 | * `/var/log` - this is required (with write permissions) in order to boot into read-only snapshots through `grub-btrfs`.
174 | * `/home` - this is required (with write permissions) in order to boot into typical desktop environments like KDE plasma.
175 | * `/boot` (and perhaps `/boot/efi` if encrypted) - this is required also from `grub-btrfs` but should already have been set up by the debian installer and should already be in your /`etc/fstab` if you followed the screenshots from the previous section.
176 |
177 | **Optionally** but highly recommended, you might want to add:
178 |
179 | * `/tmp` - you don't want to be snapshotting temporary files.
180 | * If you use virtualization software such as docker, virt manager, virtualbox, etc. you will probably want to put their files under separate subvolumes too, or perhaps symlink the paths where they put files to a different non-BTRFS partition. These are paths like `/var/lib/libvirt`, `/var/lib/docker`, or `/home//VirtualBox\040VMs`. Note that for docker in specific (which already does COW for their images), you'll need some additional configurations - see [this post](https://linuxconfig.org/how-to-move-docker-s-default-var-lib-docker-to-another-directory-on-ubuntu-debian-linux) for more info.
181 | * If you use some programming language like Python / R / etc., you probably wouldn't want all of their user-installed environments and libraries to be put into your snapshotted subvolume either.
182 |
183 | ## Mounting the volume under `/btrfsroot`
184 |
185 | (Note: this name `btrfsroot` is rather unorthodox but is what `snapper-rollback` uses by default)
186 |
187 | As a first step, you'll need to add the logical volume where your BTRFS subvolumes are going to be placed under a separate mount point that will be configured for `snapper-rollback` to use later on.
188 |
189 | * First create the mounting path as named above:
190 | ```shell
191 | sudo mkdir -p /btrfsroot
192 | ```
193 | * Find out what's the ID or the name of your main partition as used by `fstab`. It's typically something like `/dev/sda1` or `/dev/nvme0n1p1`; or if using an encrypted volume, something like `/dev/mapper/lvm0-main`. To find out:
194 | ```shell
195 | df --output=source / | tail -n 1
196 | ```
197 | (you migh want to assign that name to some environment variable for the rest of this guide)
198 | * Now put what BTRFS calls subvolume id=5 there:
199 | ```shell
200 | printf "$(df --output=source / | tail -n 1) /btrfsroot btrfs defaults,subvolid=5 0 0\n" | sudo tee -a /etc/fstab
201 | ```
202 | * Let your system reload the partition structure after editing `/etc/fstab`
203 | ```shell
204 | sudo mount /btrfsroot
205 | ```
206 | (ignore the warning message that you'll get about `systemctl daemon-reload`. Or issue the command in question from the warning if you want)
207 |
208 | **A word of warning:** unless using disk encryption, the code above will hard-code device names and numbers, such as `/dev/sda1`. The mappings from hardware to device nicknames might potentially change if the underlying hardware changes (e.g. by adding extra disks or moving them to a different connector in the motherboard), in which case the configuration will become invalid. For a more consistent configuration when physical changes are expectable, one can write device UUIDs to `/etc/fstab` instead. In order to find out the UUID of a given device, one can issue a command like the following:
209 | ```shell
210 | sudo blkid
211 | ```
212 |
213 | E.g. if following the earlier commands, and one is only interested in the UUID:
214 | ```shell
215 | sudo blkid $(df --output=source / | tail -n 1) --output=export | grep "^UUID="
216 | ```
217 |
218 | The output `UUID=` as it comes from that command can be put in the `/etc/fstab` file as the entry at the beginning of a given line in place of `/dev/`.
219 |
220 | ## Creating the structure
221 |
222 | _Note: the `@` in the subvolumes is just a naming convention. One can name the subvolumes differently if needed._
223 |
224 | ([Another similar guide with more details](https://www.jwillikers.com/btrfs-snapshot-management-with-snapper))
225 |
226 | ### `/home`
227 |
228 | **IMPORTANT!!! This guide is for Debian, which names the root subvolume as '@rootfs'. Other systems like Arch name it just '@'. Don't use '@rootfs' if that's not how your distribution's boot configuration names it.**
229 |
230 | It's a bit complicated to move `/home` and its contents into a separate subvolume in a system that's already running. The following might nevertheless help **assuming that this is a single-user machine**:
231 |
232 | * Create a subvolume for `/home`:
233 | ```shell
234 | sudo btrfs subvol create /btrfsroot/@home
235 | ```
236 | * Shallow-copy your current home directory there:
237 | ```shell
238 | sudo cp -R --reflink=always /home/$(whoami) /btrfsroot/@home
239 | ```
240 | * Give it the right permissions and ownership for your user:
241 | ```shell
242 | sudo chown -R $(whoami):$(whoami) /btrfsroot/@home/$(whoami)
243 | ```
244 | * Add it to `/etc/fstab`:
245 | ```shell
246 | printf "$(df --output=source / | tail -n 1) /home btrfs defaults,subvol=@home 0 0\n" | sudo tee -a /etc/fstab
247 | ```
248 | * Reboot the system:
249 | ```shell
250 | sudo shutdown -r now
251 | ```
252 | (note: you might also do it through the desktop environment, or with `reboot` or `systemctl reboot` depending on OS version)
253 | * After booting back and logging in again into the **new** subvolume used as home, remove the old `/home` files that are not going to be used (we now have the copy generated earlier):
254 | ```shell
255 | sudo rm -R /btrfsroot/@rootfs/home/$(whoami)
256 | ```
257 |
258 | _Note: The same trick can also be used for other user-owned paths that you might want to transfer to a separate subvolume, such as `/home/${USER}/anaconda3` if you use Anaconda. You won't need a restart for it though._
259 |
260 | ### Other subvolumes
261 |
262 | One can use the same instructions above without the change in ownership in order to swap more system paths to their own subvolume. Might not need to restart the computer for it depending on the path.
263 |
264 | In order to put `/var/log` into a separate subvolume (required by `grub-btrfs`):
265 |
266 | * Create a subvolume for it:
267 | ```shell
268 | sudo btrfs subvol create /btrfsroot/@var@log
269 | ```
270 | * Optionally but highly recommended, shallow-copy the current contents there:
271 | ```shell
272 | sudo cp -RT --reflink=always /var/log /btrfsroot/@var@log
273 | ```
274 | (ignore the errors)
275 | * Add this to your fstab:
276 | ```shell
277 | printf "$(df --output=source / | tail -n 1) /var/log btrfs defaults,subvol=@var@log 0 0\n" | sudo tee -a /etc/fstab
278 | ```
279 | * Remount:
280 | ```shell
281 | sudo systemctl daemon-reload
282 | sudo mount /var/log
283 | ```
284 | * Remove the old contents:
285 | ```shell
286 | sudo rm -rf /btrfsroot/@rootfs/var/log/*
287 | ```
288 |
289 | You might want to repeat the process for `/tmp`, but **note that it might require a computer restart** instead of a simple remount:
290 |
291 | ```shell
292 | sudo btrfs subvol create /btrfsroot/@tmp
293 | sudo cp -RT --reflink=always /tmp /btrfsroot/@tmp
294 | printf "$(df --output=source / | tail -n 1) /tmp btrfs defaults,subvol=@tmp 0 0\n" | sudo tee -a /etc/fstab
295 | sudo shutdown -r now
296 | ## <<< restart >>>
297 | sudo rm -rf /btrfsroot/@rootfs/tmp/*
298 | sudo rm -rf /btrfsroot/@rootfs/tmp/.*
299 | # (ignore the error message after the last command)
300 | ```
301 |
302 | **************
303 | By this point, your file `/etc/fstab` should now have separate BTRFS subvolumes with the following entries and paths:
304 |
305 | * `subvolid=5` -> `/btrfsroot`
306 | * `subvol=@home` -> `/home`
307 | * `subvol=@var@log` -> `/var/log`
308 | * `subvol=@tmp` -> `/tmp` (optional but highly recommended)
309 |
310 | # Installing and configuring software for snapshots and rollbacks
311 |
312 | As per the beginning of this guide, you'll need the following 3 key pieces of software:
313 |
314 | * `snapper`
315 | * `grub-btrfs`
316 | * `snapper-rollback`
317 |
318 | And as a reminder, in order to install all of these, you'll first need a few dependencies along the way:
319 | ```shell
320 | sudo apt-get install btrfs-progs python3-btrfsutil gawk inotify-tools make build-essential git
321 | ````
322 |
323 | ## 1. Snapper
324 |
325 | `snapper` itself can be easily installed from the debian main repository:
326 |
327 | ```shell
328 | sudo apt-get install snapper
329 | ```
330 |
331 | You might perhaps also want either `snapper-gui` (note that you'll need to execute it as root in order for it to show you non-user partitions) or [btrfs-assistant](https://gitlab.com/btrfs-assistant/btrfs-assistant), which provide graphical interfaces over `snapper`.
332 |
333 | After installing snapper, we can now follow [the Arch wiki](https://wiki.archlinux.org/title/Snapper) steps for getting it to take periodic snapshots of the system BTRFS partition (you _might_ optionally configure a similar thing for your `/home` subvolume):
334 |
335 | * Monitor and create snapshots from the root of the file system:
336 | ```shell
337 | sudo snapper -c root create-config /
338 | ```
339 | * The default for `snapper` is to put the snapshots it takes under a folder named `/.snapshots` under the same path that it is snapshotting. In our case, we'll want that to be under a different BTRFS subvolume. **If you already had snapshots**, you'll need to remove them following [the Arch wiki](https://wiki.archlinux.org/title/Snapper#Suggested_filesystem_layout), or if it doesn't work, then [this guide](https://www.jwillikers.com/btrfs-snapshot-management-with-snapper).
340 | * Now proceed with creating a subvolume for the snapshots:
341 | ```shell
342 | sudo btrfs subvol create /btrfsroot/@snapshots
343 | ```
344 | * Create a path `/.snapshots` where to mount this new subvolume with the snapshots that it will take:
345 | ```shell
346 | sudo mkdir -p /.snapshots
347 | ```
348 | * Mount the snapshots subvolume where it needs to be:
349 | ```shell
350 | printf "$(df --output=source / | tail -n 1) /.snapshots btrfs defaults,subvol=@snapshots 0 0\n" | sudo tee -a /etc/fstab
351 | sudo mount /.snapshots
352 | ```
353 |
354 | ### 1.1 Optional: better snapshot titles
355 |
356 | By default, the snapshots that snapper will take after installing or uninstalling packages in Debian will be named as "apt" + pre/post. It's nevertheless possible to have them use more informative names, such as the command that triggered the snapshot creation (e.g. `apt-get install `) by modifying the file `/etc/apt/apt.conf.d/80snapper`.
357 |
358 | See this gist for a modification that will make it include the command names:
359 | https://gist.github.com/imthenachoman/f722f6d08dfb404fed2a3b2d83263118
360 |
361 | ## 2. Grub-BTRFS
362 |
363 | `grub-btrfs` is not yet (as of 2023-04) available from the debian main repository, but can be installed from GitHub.
364 |
365 | **Be sure to install from the master branch**, as the release-level versions are no longer compatible with the latest debian at the time of writing.
366 |
367 | * First clone the repository:
368 | ```shell
369 | git clone https://github.com/Antynea/grub-btrfs.git
370 | ```
371 | * Now verify that it's possible to build it:
372 | ```shell
373 | cd grub-btrfs
374 | sudo make
375 | ```
376 | * If that succeeded, then go ahead and install:
377 | ```shell
378 | sudo make install
379 | ```
380 | * Once installed, enable and start the daemon from this software:
381 | ```shell
382 | sudo systemctl enable grub-btrfsd
383 | sudo systemctl start grub-btrfsd
384 | ```
385 | * Update grub to use the new config:
386 | ```shell
387 | sudo update-grub
388 | ```
389 | (_Note: you might get a warning about no snapshots being found. That's fine as there aren't any yet if you followed this guide on a clean system_)
390 |
391 | ## 3. Snapper-Rollback
392 |
393 | Also needs to be installed from Git:
394 | ```shell
395 | cd .. # if you were inside the previous git repo
396 | git clone https://github.com/jrabinow/snapper-rollback.git
397 | cd snapper-rollback
398 | sudo cp snapper-rollback.py /usr/local/bin/snapper-rollback
399 | sudo cp snapper-rollback.conf /etc/
400 | ```
401 | (**IMPORTANT!!** the readme in that project recommends copying it to `/usr/local/sbin`, while this puts it under `/usr/local/bin`. Reason being: `/usr/local/sbin` might not be added in yout `$PATH` env. variable. Verify that the path where you copy it into is shown among the entries that you see from `echo ${PATH}`)
402 |
403 | **Now that it is installed**, you'll need to modify its configuration file (the one that was copied into `/etc/snapper-rollback.conf` in the last command above)
404 |
405 | Notice that, if you open the file, there will be a section like the following:
406 | ```
407 | # config for btrfs root
408 | [root]
409 | # Name of your linux root subvolume
410 | subvol_main = @
411 | ```
412 |
413 | Since we are using **Debian**, the main subvolume will be named `@rootfs` instead of `@`. Thus, it's necessary to edit that line to make it look like this:
414 | ```
415 | # config for btrfs root
416 | [root]
417 | # Name of your linux root subvolume
418 | subvol_main = @rootfs
419 | ```
420 |
421 | To do it programmatically:
422 | ```shell
423 | sudo sed -i 's/subvol_main = @/subvol_main = @rootfs/g' /etc/snapper-rollback.conf
424 | ```
425 |
426 | *****************
427 |
428 | With these 3 pieces of software already installed, now reboot the machine. Afterwards, **the system should now be fully configured for snapshots and rollbacks**.
429 |
430 | # Performing a system rollback
431 |
432 | In order to verify that the snapshotting and restoration are working correctly, it's a good idea to try out a rollback.
433 |
434 | **Disclaimer:** this guide uses `snapper-rollback`, which is a small external script from [this repository](https://github.com/jrabinow/snapper-rollback). The `snapper` software also comes with a built-in `rollback` command, but the two are not equivalent - see [this post](https://github.com/jrabinow/snapper-rollback/issues/16) for a description about their differences.
435 |
436 | As a first step, in order to convince yourself that the rollback has been successful, first install some new software that isn't already in the system through something like `apt`, `apt-get`, `aptitude` or similar. For example, if installing debian, it typically doesn't come with the `atop` software, so install it in order to try:
437 | ```shell
438 | sudo apt-get install atop
439 | ```
440 | (choose a different software if you already have it installed)
441 |
442 | Verify that your system can now run the `atop` that you just installed by executing it:
443 | ```shell
444 | atop
445 | ```
446 | Then exit from the program with Ctrl+C.
447 |
448 | Once that is done, notice that your system will have created two snapshots (before/after `apt` command). You can verify this by issuing a command like the following:
449 | ```shell
450 | sudo update-grub
451 | ```
452 | This time, it should emit some prints about having found those snapshots, which _might_ look like this:
453 | ```
454 | ...
455 | Found snapshot: | @snapshots/2/snapshot | post | apt
456 | Found snapshot: | @snapshots/1/snapshot | pre | apt
457 | ...
458 | ```
459 | Note that, if `grub-btrfs` is working correctly, it should run `update-grub` automatically after it finds the new snapshots, so this is step is not strictly needed but can give you a visual clue of whether things went smoothly.
460 |
461 | Now it should be possible to boot into those snapshots. In particular, the snapshot saying "pre" (number "1" above) should not have `atop` installed. So now restart the computer, and pick this new option in the GRUB menu:
462 |
463 | 
464 |
465 | Now choose your first entry that says "pre" in the subsequent menu. **Make a note of which number it was** (here it is number "1"). You will need to remember this number for later:
466 | 
467 |
468 | And once inside it, choose the only linux kernel version that it will have:
469 | 
470 |
471 | Now you should have booted into a **READ-ONLY** snapshot of your system at the time before `atop` was installed. Verify right there that `atop` is not installed anymore in this snapshot:
472 | ```shell
473 | atop
474 | ```
475 | (should error out as it won't be installed)
476 | ```
477 | bash: atop: command not found
478 | ```
479 |
480 | Now, before the final rollback, perform a dry-run where you will see the commands that the rollback program will issue. Assuming that the snapshot you want to restore is number "1" (change it to your desired snapshot number otherwise), this will first ask you for a confirmation, and then show what it will execute if you puruse the **real** rollback:
481 | ```shell
482 | snapper-rollback 1 --dry-run
483 | ```
484 |
485 | If everything looks Ok, **now perform the actual rollback:**
486 | ```shell
487 | sudo snapper-rollback 1
488 | ```
489 |
490 | By this point, you can reboot the system - next it starts, it will boot from the previous snapshot that you just restored here when you select the first entry in the GRUB boot menu. Only this time, it will be read+write as usual.
491 |
492 | Notice that part of what the command did was to move what's the current snapshot called `@rootfs` to a new snapshot called `@rootfs`, which if following the `fstab` structure of this guide, will be findable under `/btrfsroot`. **This old unused snapshot doesn't have an auto-delete policy** like the other auto-created snapper snapshots, so you will have to delete it manually after having rebooted into the rolled-back system:
493 | ```shell
494 | find /btrfsroot -maxdepth 1 -type d -name '@rootfs[0-9]*' -exec sudo rm -Rf {} +
495 | ```
496 |
497 | **Note:** you can also delete it visually through software like `snapper-gui` or `btrfs-assistant` - for example, assuming `snapper-gui` was installed (`sudo apt-get install snapper-gui`), can be launched with root priviliges for this operation as follows:
498 | ```shell
499 | sudo snapper-gui
500 | ```
501 |
502 | `btrfs-assistant` will ask for the sudo password on launch, so it's not necessary to launch it with elevated permissions from the start. Assuming a system-wide install from their source repository, can be launched as follows:
503 | ```shell
504 | btrfs-assistant-launcher
505 | ```
506 |
507 | # Caution: booting snapshots and kernels
508 |
509 | A word of caution: note that `/boot` is a separate partition from the main partition that was used for the BTRFS subvolumes, and is shared across all subvolumes, including the snapshots. When a new version of the linux kernel gets installed, it registers itself by creating an entry in `/boot`, even though the kernel is installed in a subvolume of the system's root partition (`/`). Hence, when attempting to boot from a snapshot, it will show a menu with selectable linux kernel versions to boot, but those versions might not necessarily be installed in the snapshot that one wants to boot from - one needs to be careful to select a kernel version that would be installed in the snapshot, as otherwise it will lead to boot errors.
510 |
511 | Similarly, if performing a rollback to an older snapshot after installing a newer kernel version, it will not clean up these new version entries in the boot menu for kernel versions - be mindful that by default it will try to boot the latest version of the kernel available from `/boot`, which can result in a non-bootable default after a rollback if the snapshot didn't have the latest kernel version. In such cases, one first needs to boot from an available kernel version through entry "Advanced options for Debian GNU/Linux" in the boot menu, and then clean up the missing `/boot` entries through `sudo update-grub`.
512 |
513 | # Snapshots for the `/home` subvolume
514 |
515 | Just like it was done for the root of the file system `/` (subvolume `@rootfs`), it's also possible to let snapper automatically create daily snapshots of the `/home` subvolume and keep the last N of them. There are a couple caveats however:
516 |
517 | * Snapshots are created in read-only mode, while typical desktop environments such as KDE plasma are unable to log into a non-writable `/home/` path. Thus, booting into a snapshot of `/home` will first require making it writable, and writable snapshots do not share the same space efficiency optimizations as non-writable ones under a COW system.
518 | * Snapshots of `/home` will not necessarily coincide with snapshots of `/` in terms of the times at which they are taken.
519 | * Using a snapshot of `/home` requires editing the current `fstab` file for it, thus one cannot easily boot into an old snapshot of `/` alongside with an old snapshot of `/home` (as it requires modifying the `fstab` of the snapshot into which you will boot).
520 |
521 | It's nevertheless handy to have a back up when things do wrong, even if it's difficult to use.
522 |
523 | Steps:
524 |
525 | * Let `snapper` manage snapshots for yout `@home` subvolume:
526 | ```shell
527 | sudo snapper -c home create-config /home
528 | ```
529 | * As before, snapper creates the snapshots under a subfolder `/.snapshots` in the same path that is being snapshotted, which now will be `/home/.snapshots` instead of `/.snapshots`. We'll first need to create yet another subvolume for these snapshots and mount it under the path that snapper will use:
530 | ```shell
531 | sudo btrfs subvol create /btrfsroot/@homesnapshots
532 | printf "$(df --output=source / | tail -n 1) /home/.snapshots btrfs defaults,subvol=@homesnapshots 0 0\n" | sudo tee -a /etc/fstab
533 | sudo mkdir -p /home/.snapshots
534 | sudo mount /home/.snapshots
535 | ```
536 | * As these aren't auto-update by `apt` and we don't want to wait a long time for a "timeline" snapshot, generate a manual snapshot right there:
537 | ```shell
538 | sudo snapper -c home create --description myfirstsnapshot
539 | ```
540 | * In order to verify that snapshot rollbacks are working, create some new file under your home folder that would not be part of the snapshot just taken:
541 | ```shell
542 | touch ~/deleteme.txt
543 | ```
544 | * Give the snapshot write permissions:
545 | ```shell
546 | sudo btrfs property set -ts /home/.snapshots/1/snapshot ro false
547 | ```
548 | * Edit your `fstab` to have that particular snapshot as the mount point for `/home`. Where it currently says:
549 | ```
550 | subvol=@home
551 | ```
552 | Replace with:
553 | ```
554 | subvol=@homesnapshots/.snapshots/1/snapshot
555 | ```
556 | * Reboot the system - e.g.:
557 | ```shell
558 | sudo shutdown -r now
559 | ```
560 |
561 | It should now have booted into the old home snapshot. Verify this by noticing that it doesn't have the file named `deleteme` under your home folder.
562 |
563 | * If you want to now go back to the actual `/home` instead of the snapshot, then edit back the `fstab` file to how it was at the beginning and then reboot.
564 | * Don't forget to clean up the snapshot folder as it won't be auto-removed the same way "timelined" snapshots are. **After rebooting** into the mainline (non-snapshot) `/home` (can also be done from `snapper-gui` or `btrfs-assistant`):
565 | ```shell
566 | sudo rm -Rf /home/.snapshots/1/snapshot
567 | ```
568 |
569 | * If you would like to take this as your current `/home` snapshot and remove the old one, then:
570 |
571 | * Move away the snapshot called `@home`:
572 | ```shell
573 | sudo mv /btrfsroot/@home /btrfsroot/@home_old
574 | ```
575 |
576 | * Set the current snapshot as `@home` snapshot:
577 | ```shell
578 | sudo btrfs subvol snapshot /btrfsroot/@homesnapshots/1/snapshot /btrfsroot/@home
579 | ```
580 |
581 | * Edit back your `/etc/fstab` file to have the `/home` path mounted like this:
582 | ```
583 | subvol=@home
584 | ```
585 |
586 | * Reboot - e.g.:
587 | ```shell
588 | sudo shutdown -r now
589 | ```
590 |
591 | * Remove the old `/home` snapshot (can also be done from `snapper-gui` or `btrfs-assistant`):
592 | ```shell
593 | sudo rm -Rf /btrfsroot/@home_old
594 | ```
595 |
596 | * Remove the snapshot of what is now the current home (can also be done from `snapper-gui` or `btrfs-assistant`):
597 | ```shell
598 | sudo rm -Rf /btrfsroot/@homesnapshots/.snapshots/1/snapshot
599 | ```
600 |
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