Felitendo
0f91a79ba6
A machine switched off mid-update leaves /var/lib/pacman/db.lck behind. Nothing removed it, so every subsequent run deferred on it - one power cut would have stopped updates permanently and silently, which on an unattended machine is the worst outcome there is. A lock older than the current boot is provably abandoned: no process that could hold it still exists. Those are now removed and the interrupted upgrade is repeated, with pacman reinstalling anything caught half-written. A lock that is merely unheld within the same boot stays untouched and is only reported, since removing it could corrupt a live transaction; the boot-time test is what makes the difference between a proof and a guess. A fuser check is kept alongside it so a backwards clock jump cannot make a live lock look abandoned. Documented what each layer can actually promise: suspend and normal shutdown are blocked by the existing inhibitor, a hard power-off cannot be prevented by anything, and snap-pac's pre/post snapshots remain the backstop.
149 lines
5.3 KiB
Scdoc
149 lines
5.3 KiB
Scdoc
cachy-auto-update(1)
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# NAME
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cachy-auto-update - unattended background updates for CachyOS
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# SYNOPSIS
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*cachy-auto-update* [_command_] [_options_]
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# DESCRIPTION
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*cachy-auto-update* keeps a CachyOS machine current without anybody having to
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think about it: repository packages, AUR packages, Flatpaks and AppImages are
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updated in the background, with no password prompt and no terminal.
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Run without a command it opens a small interactive menu with the two switches
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that matter - automatic updates on/off and notifications on/off - plus the
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current status.
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The actual work is done by a systemd system service. The timer ticks hourly;
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whether a tick does anything is decided by _UpdateInterval_ (daily by default).
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A run that is postponed - low battery, a game running, somebody else using
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pacman - is simply retried at the next tick.
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# COMMANDS
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*enable*
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Turn automatic updates on and enable the systemd timer.
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*disable*
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Turn automatic updates off and stop the timer.
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*notifications* on|off
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Turn desktop notifications on or off.
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*status*
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Show the current state plus an evaluation of every condition that can
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postpone a run. This is the first thing to look at when the updater
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appears to be doing nothing.
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*run* [--force] [--dry-run]
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Update now. *--force* skips the interval, battery and gaming checks;
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*--dry-run* lists what would be updated and changes nothing. The check
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for another running package manager is never skipped.
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*log* [-n _num_] [-f] [-a]
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Show the log of the last run. *-a* shows the rolling log instead, *-f*
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follows it.
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*-h*, *--help*
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Show a short help text.
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*-V*, *--version*
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Show the version.
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# CONDITIONS
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Before anything is installed, a run is postponed when:
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- the battery is below _MinBatteryPercent_ (ignored on mains power, and on
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machines without a battery);
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- _RequireAC_ is set and the machine is not plugged in;
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- a game is running - detected via GameMode, a list of known game processes, or
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an application holding a blocking idle inhibitor;
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- pacman's database is locked, or pacman, yay, paru, pamac or a similar tool is
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running.
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The last check is what keeps *cachy-auto-update* out of the way of manual
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package management. It cannot work in the other direction: if a manual pacman
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run starts while an update is already in flight, that run will report the usual
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locked-database error.
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# HOW UPDATES ARE APPLIED
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Repository packages are updated with *pacman -Syu --noconfirm*, but only after
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*checkupdates*(8) has confirmed there is something to do, so on a quiet day
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pacman's lock is never taken at all.
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A package that has to replace another one is handled silently. If pacman would
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stop to ask whether a conflicting package may be removed, the transaction is
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retried once with that question answered affirmatively, unless
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_AutoResolveConflicts_ is turned off. Files on disk that collide with a package
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are *not* forced - that stays a human decision. A signature failure triggers one
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keyring refresh and one retry.
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AUR packages are built and installed as the locked *cachy-auto-update* system
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account, because *makepkg*(8) refuses to run as root. That account has no
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password and no shell, and is allowed - through _/etc/sudoers.d/cachy-auto-update_
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- to invoke *pacman* without one. No user password is ever stored anywhere.
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A failed AUR build is not reported the first time it happens; only a failure
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that repeats is worth waking somebody up for.
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Flatpak system installations are updated directly as root, user installations
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inside each user's own account. AppImages are updated through Gear Lever, for
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users with a graphical session, and AppImages whose application is currently
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running are skipped.
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The machine is never restarted automatically. When a kernel update makes a
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restart necessary, a notification says so.
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# INTERRUPTED UPDATES
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While a transaction is running, *cachy-auto-update* holds a
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*systemd-inhibit*(1) lock on _sleep_ and _shutdown_ in blocking mode, so a
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suspend, a lid close or a normal shutdown request cannot cut it short.
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A hard power-off - holding the power button, or losing mains power - is not
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preventable. On the next run a leftover _/var/lib/pacman/db.lck_ is removed if
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it is older than the current boot, since no process able to hold it can still
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exist; the upgrade is then repeated and pacman reinstalls whatever was caught
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half-written. A lock file that is unheld but was created during the current
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boot is reported rather than removed, because there is no way to prove it is
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abandoned.
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Without that recovery a single power cut would leave a lock that makes every
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subsequent run defer, silently stopping updates for good.
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On Btrfs with *snapper*(8) and *snap-pac*, each pacman transaction is bracketed
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by a pre and post snapshot, so a broken upgrade remains rollbackable.
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# FILES
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_/etc/cachy-auto-update/cachy-auto-update.conf_
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Configuration. See the comments in the file itself for every option.
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_/etc/sudoers.d/cachy-auto-update_
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Lets the build account call pacman without a password.
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_/var/log/cachy-auto-update/last-run.log_
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Full output of the most recent run.
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_/var/log/cachy-auto-update/cachy-auto-update.log_
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Rolling log across runs.
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_/var/lib/cachy-auto-update/_
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State: timestamps, counters, queued notifications.
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# SEE ALSO
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*pacman*(8), *checkupdates*(8), *paru*(8), *yay*(8), *flatpak*(1),
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*systemd.timer*(5)
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# AUTHOR
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Felitendo. Source and bug reports:
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https://github.com/Felitendo/cachy-auto-update
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