usysconf-epoch: Finalise

[silkeh]

Summary

Finalise the usysconf-epoch script:

• Run it through shellcheck.

• Actually delete orphaned files after backup.

• Add a CLI flag for testing in a VM without rebooting.

• Special case kernel module dep/map files.

• Add support for an eopkg flag file and an epoch flag file.

• Show a message while the script runs:

  usysconf-progress-2024-08-07_18.49.56.mp4

Note that the epoch script depends on the work in getsolus/eopkg#78 and getsolus/eopkg#79. The script is behind feature flags (see below), so it is safe to merge.

Test Plan

Tested in a VM with various disk limits:

Profile	MB/s	IOPS	Normal boot	Script
Slow HDD	10	55	1min 57s	1min 0s
Fast HDD	100	150	56s	20s
SATA SSD	500	85.000	4s	1s

Enabled by editing /etc/sysconfig/epoch with:

I_UNDERSTAND_THAT_THIS_SCRIPT_CAN_BREAK_MY_SYSTEM=1
I_WANT_TO_TEST_THE_EPOCH_TRANSITION_WORKS=1

Checklist

• Package was built and tested against unstable

[EbonJaeger]

This question may be out of scope for this PR, but if a user is experiencing an issue or slowness, is there actually anything that we can ask them or get them to provide to try to figure out why?

[silkeh]

but if a user is experiencing an issue or slowness, is there actually anything that we can ask them or get them to provide to try to figure out why?

Yeah, the script logs what it's doing. If a user can retrieve the logs using boot rescue after the 10 minute timeout we can probably see if it's processing files that we didn't expect.

[silkeh]

Merging this so I can follow it up in the next PR.