Saving Package Set Snapshots
Arch Linux (and Linux in general) used to have a reputation of breaking every
time packages were upgraded. Around 2010, Aura's author used to run Arch on a
Macbook, and such catastrophic breakage did occur every six months or so. But
fast-forward to the present day, and such problems are rare. Even so, the idea
of "whole system rollback" is spreading, and even since those early Arch-on-Mac
days, Aura has had the -B Command for saving and restoring entire package
sets.
Saving a Package Set
> sudo aura -B
aura >>= Saved package state.
This saves a file like 2020.06(Jun).14.08.56.46.json to
/var/cache/aura/states/. If we take a peek inside, we see:
> cat 2020.06\(Jun\).14.08.56.46.json | aeson-pretty | head
{
"time": "2020-06-14T08:56:46.437911573-07:00",
"pinned": false,
"packages": {
"rasqal": "1:0.9.33-3",
"java-environment-common": "3-3",
"kwallet": "5.70.0-1",
"python2-livereload": "2.6.1-1",
"nethogs": "0.8.6-1",
"coreutils": "8.32-1",
Simple enough - a list of all installed packages with their versions. We'll talk
about pinned below.
These files are in JSON format in case other tools wish to read them.
Restoring a Package Set
I performed a big -Syu of about 250 packages, but wish to roll them all back
to the saved state I just made above. Let's see that happen:
> sudo aura -Br
1. /var/cache/aura/states/2018.07(Jul).06.10.03.18.json
2. /var/cache/aura/states/2020.05(May).04.09.15.57.json
3. /var/cache/aura/states/2020.05(May).11.11.30.35.json
... many choices ...
49. /var/cache/aura/states/2020.06(Jun).12.10.23.12.json
50. /var/cache/aura/states/2020.06(Jun).14.08.56.46.json
51. /var/cache/aura/states/2020.06(Jun).14.09.03.59.json
>> 51
aura >>= Requested downgrade versions not available for:
lib32-libdrm
libdrm
libretro-nestopia
linux-firmware
portaudio
runc
spandsp
virtualbox
vlc
xine-lib
resolving dependencies...
looking for conflicting packages...
Package (234) Old Version New Version Net Change
acorn 1:7.3.1-1 1:7.2.0-1 0.00 MiB
alsa-lib 1.2.3-1 1.2.2-1 -0.01 MiB
alsa-topology-conf 1.2.3-1 1.2.2-2 -0.19 MiB
alsa-ucm-conf 1.2.3-1 1.2.2-1 -0.02 MiB
alsa-utils 1.2.3-1 1.2.2-1 0.00 MiB
... etc ...
wine 5.10-1 5.9-1 -1.26 MiB
x265 3.4-1 3.3-1 -0.01 MiB
xkeyboard-config 2.30-1 2.29-1 0.09 MiB
Total Installed Size: 3315.10 MiB
Net Upgrade Size: -38.46 MiB
:: Proceed with installation? [Y/n]
... downgrading ...
It all went smoothly, even rolling back the kernel. Notice that Aura will warn you if it couldn't find certain versions to roll back to.
Clearing out old Saved States
50 saved states is a little much. I probably don't even have most of the
packages necessary to roll back to those early states, since I use -Cc often.
Let's clear out the old ones:
> sudo aura -Bc 5
aura >>= You currently have 52 saved package states.
aura >>= 1 of these are pinned, and won't be removed.
aura >>= Most recently saved: 2020.06(Jun).14.09.17.09.json
aura >>= 5 package states will be kept. Remove the rest? [Y/n]
And sure enough, only the most recent remain:
> sudo aura -Br
1. /var/cache/aura/states/2018.07(Jul).06.10.03.18.json
2. /var/cache/aura/states/2020.06(Jun).12.10.22.56.json
3. /var/cache/aura/states/2020.06(Jun).12.10.23.12.json
4. /var/cache/aura/states/2020.06(Jun).14.08.56.46.json
5. /var/cache/aura/states/2020.06(Jun).14.09.03.59.json
6. /var/cache/aura/states/2020.06(Jun).14.09.17.09.json
>>
Hey wait, what is that state from 2018 still doing there? Notice:
aura >>= 1 of these are pinned, and won't be removed.
Now we can talk about pinning.
Pinning a Saved State
If we don't want a certain package state to be removed by -Bc no matter what,
we can pin it. There is no flag for this, we need to open the .json file of
the state we wish to pin, and change its pinned field from false to true.