Bug#1041730: dpkg: Systemd dpkg-db-backup.timer unit should be "Persistent=true"

[Teemu Likonen]

Package: dpkg
Version: 1.21.22
Severity: minor
Tags: patch
X-Debbugs-Cc: tliko...@iki.fi

Dpkg installs systemd timer unit dpkg-db-backup.timer which is supposed
to run daily:

    # /lib/systemd/system/dpkg-db-backup.timer
    [Unit]
    Description=Daily dpkg database backup timer
    Documentation=man:dpkg(1)

    [Timer]
    OnCalendar=daily

    [Install]
    WantedBy=timers.target

The "OnCalendar=daily" rule means every night exactly at 00:00:00. The
timer does not trigger if computer is not turned on exactly at that
time.

I think the timer is meant to trigger daily even if the computer is not
running at midnight. The attached patch makes the timer trigger
immediately if the specified time has passed (Persistent=true).


-- Package-specific info:
This system uses merged-usr-via-aliased-dirs, going behind dpkg's
back, breaking its core assumptions. This can cause silent file
overwrites and disappearances, and its general tools misbehavior.
See <https://wiki.debian.org/Teams/Dpkg/FAQ#broken-usrmerge>.

-- System Information:
Debian Release: 12.0
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 6.1.0-10-amd64 (SMP w/8 CPU threads; PREEMPT)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, 
TAINT_UNSIGNED_MODULE
Locale: LANG=fi_FI.UTF-8, LC_CTYPE=fi_FI.UTF-8 (charmap=UTF-8), LANGUAGE=fi
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages dpkg depends on:
ii  libbz2-1.0   1.0.8-5+b1
ii  libc6        2.36-9
ii  liblzma5     5.4.1-0.2
ii  libmd0       1.0.4-2
ii  libselinux1  3.4-1+b6
ii  libzstd1     1.5.4+dfsg2-5
ii  tar          1.34+dfsg-1.2
ii  zlib1g       1:1.2.13.dfsg-1

dpkg recommends no packages.

Versions of packages dpkg suggests:
ii  apt            2.6.1
pn  debsig-verify  <none>

-- no debconf information

--- debian/dpkg.dpkg-db-backup.timer~   2023-07-22 19:18:00.760386969 +0300
+++ debian/dpkg.dpkg-db-backup.timer    2023-07-22 19:17:27.881116417 +0300
@@ -4,6 +4,7 @@
 
 [Timer]
 OnCalendar=daily
+Persistent=true
 
 [Install]
 WantedBy=timers.target