Add instructions for snapshottable Tails VMs under Linux

[rmol]

Status

Ready for review

Description of Changes

The same installer hacks used with Tails under VirtualBox on Macs enable its installation on a snapshottable QCOW2-backed libvirt VM, so add that as an option under Linux in the Tails virtualization docs.

Testing

• Check out this branch.
• Run make docs.
• Visit http://localhost:8000/development/virtualizing_tails.html#linux
• Read the revised section critically.

If you use libvirt on Linux:

• Follow the steps under http://localhost:8000/development/virtualizing_tails.html#enabling-snapshots to create a Tails VM.
• Boot Tails
• Create a file under ~/Persistent.
• Use virt-manager to create a snapshot of the VM.
• Remove the file.
• Use virt-manager to revert to the snapshot.
• The file should be present again.

Deployment

Docs only.

Checklist

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

If you made changes to documentation:

• Doc linting (make docs-lint) passed locally

[eloquence]

Test flake #4691, kicking CI. However, this branch should ideally be prefixed docs- to avoid running the whole CI suite -- if significant changes are required, it may be worth re-doing under a new branch name.

[redshiftzero]

hey @kushaldas if you are doing QA in VMs, give these docs a whirl, I bet you'll find them handy

[rmol]

I've discovered the existing patches for installation and persistence don't apply cleanly on Tails 4, so further review should wait until they've been updated.

[eloquence]

I've discovered the existing patches for installation and persistence don't apply cleanly on Tails 4,

So beyond the snapshotting capability you're documenting here, our Virtualizing Tails docs are currently invalid for Macs? In that case, I think this warrants a bit higher priority than it's been getting; possibly a candidate for the next sprint.

[rmol]

I believe that's the case. I'd be happy to update the patches, but will have to ask for testing help from someone with a Mac.

[eloquence]

Note that this PR will need to be migrated to the securedrop-docs repository (assuming we still want to land it); happy to keep it open until then for visibility.

[zklosko]

@rmol I have a Mac. Do you still need assistance with testing stuff?

[rmol]

@zklosko I'd need to revisit all of this first. It's obviously not been a priority. If you found this issue because you're trying to run the admin in virtualized Tails on a Mac, let us know, but otherwise we're probably going to keep this on hold.

[zenmonkeykstop]

Closing this in favour of freedomofpress/securedrop-docs#251 - if anyone was planning to test or revise the snapshot process, please check there instead!