[Bug 1875760] Update Released

[Brian Murray]

The verification of the Stable Release Update for command-not-found has
completed successfully and the package is now being released to
-updates.  Subsequently, the Ubuntu Stable Release Updates Team is being
unsubscribed and will not receive messages about this bug report.  In
the event that you encounter a regression using the package from
-updates please report a new bug using ubuntu-bug and tag the bug report
regression-update so we can easily find any regressions.

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https://bugs.launchpad.net/bugs/1875760

Title:
  /usr/lib/cnf-update-db:sqlite3.OperationalError:/usr/lib/cnf-update-
  db at 26:create

Status in command-not-found package in Ubuntu:
  Fix Released
Status in command-not-found source package in Focal:
  Fix Released

Bug description:
  [Impact]

  The Ubuntu Error Tracker has been receiving reports about a problem
  regarding command-not-found. c-n-f- crashes when there are two
  parallel processes trying to update the tmpdb via its 'cnf-update-db'
  script. Only the first process can lock the sqlite3 database, the 2nd
  one will crash.

  There is no impact on users, but we want to avoid the noise about
  those crashes in the Ubuntu Error Tracker.

  This update ignores the update-db operation, if the database is
  already locked and logs a warning message.

  [Test Case]

   * Manually lock the database
   * Run 'cnf-update-db'
   * Verify it is not crashing

  sudo cp /var/lib/command-not-found/commands.db /var/lib/command-not-found/commands.db.tmp
  sudo sqlite3 /var/lib/command-not-found/commands.db.tmp
  SQLite version 3.31.1 2020-01-27 19:55:54
  Enter ".help" for usage hints.
  sqlite> PRAGMA locking_mode = EXCLUSIVE;
  exclusive
  sqlite> BEGIN EXCLUSIVE;
  sqlite>

  sudo rm /var/lib/command-not-found/commands.db.metadata
  sudo sudo /usr/lib/cnf-update-db --verbose
  echo $?

  [Regression Potential]

  This changes touches the 'cnf-update-db' script which creates or
  updates the sqlite database containing the mappings between
  executables and its corresponding packages. It it regresses the
  database might not be correctly updated anymore and thus users might
  not get proper package recommendations when they try to execute a non-
  installed application.

  [Original Bug Description]

  The Ubuntu Error Tracker has been receiving reports about a problem regarding command-not-found.  This problem was most recently seen with package version 20.04.2, the problem page at https://errors.ubuntu.com/problem/e1fb83cff555154efc036bf0674053c5e555d96b contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
  If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.

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