Additional Software does not recover from corrupted, incomplete, or de-synchronized APT lists

• Workaround
• Failure to recover from APT lists that are de-synchronized with the packages cache
• Failure to recover from broken APT lists

Plan to fix this: #18620 (comment 181403)

While we're at it we could solve #18657 (closed).

Workaround

1. Boot Tails

2. In the Welcome Screen, set an Administration Password and unlock your Persistent Storage

3. Start Tails

4. Wait until you see the error about Additional Software failing to install

5. Open a Root Terminal

6. Run this command:

   systemctl stop tails-additional-software-upgrade.service tails-additional-software-upgrade.path tails-additional-software-upgrade.service && \
   rm -rf /var/lib/apt/lists/* /live/persistence/TailsData_unlocked/apt/lists.old && \
   apt update

   … and wait for it to complete.

7. Restart Tails

Failure to recover from APT lists that are de-synchronized with the packages cache

See #17392 (closed), #16567 (closed), #16566 (closed).

Failure to recover from broken APT lists

Multiple users have reported to Help Desk that they receive the following error when using the Additional Software feature:

E: Splitting of clearsigned file /var/lib/apt/lists/cdn-fastly.deb.debian.org_debian_dists_buster_InRelease failed as it doesn't contain all expected parts
E: The package lists or status file could not be parsed or opened.
E: _cache->open() failed, please report.

WB reports:

• wb:aad8bfb4692e9135d97890e5bf8cde7e
• faf403d6a0fbd8e77e107440ac32ea7f: no more info than what this issue says
• fbcbff11c73c393b66d1ba5448d9d3a8:
  • error follows unclean shutdown + starting Synaptic which fails to download APT lists
  • tails-additional-software-install.service failed with the same error ("INFO] E: Splitting of clearsigned file")
  • tails-additional-software-upgrade.service runs apt update which fails to fetch the Translation-en files for a few archives (while others work just fine); the service notices the failure but I see no trace of restoring the old APT lists in the logs
• 7b2e7b5ddca8c6b44814382399e98b96
  • tails-additional-software-install.service restored old APT lists, which are corrupted too ("too" because if there are old lists, that indicates the new ones may be broken)
  • tails-additional-software-upgrade.service is not started, presumably because tails-additional-software-install.service failed: this looks incorrect, because tails-additional-software-upgrade.service is our chance to recover from such failures. Except in this case it would not have helped, because the same recovery fails with Synaptic:
  • The user started Synaptic, which failed to update or to read the APT lists
• af8ab8ff207b7a4c3a927923dea5808: no more info than what this issue says
• 1c894357e7a235c81b1b0c9772ad0e50
  • no old APT lists were found and restored: tails-additional-software-install.service fails due to corrupted APT lists