[mythtv-users] anacron time change after upgrade to Ubuntu 18.04

[Stephen Worthington]

On Tue, 6 Nov 2018 06:59:31 -0500, you wrote:

>On my backend I have 2 cron jobs I put into /etc/cron.daily for database 
>backup and optimization. The scripts email when done with the date and time.
>
>On Ubuntu 16.04 it ran around 7:35 am. After the 'do-release-upgrade' it 
>runs at 12:10 am.
>
>I always wondered why 7:35am with a /etc/crontab entry like the one 
>below, but I really can't figure out 12:10 am based on it.
>
>Any ideas?
>
>25 6    * * *    root    test -x /usr/sbin/anacron || ( cd / && 
>run-parts --report /etc/cron.daily )
>
>Jim A

If you read that crontab code carefully, you will see that what it is
doing is testing to see if an anacron executable is present, and if
so, it does not run the cron.daily tasks from crontab.  As Ubuntu does
have an anacron executable present, those crontab entries do nothing,
and it is left to anacron to run the /etc/cron.daily, /etc/cron.weekly
and /etc/cron.monthly tasks.  The /etc/cron.hourly tasks, however are
run from crontab.

In Ubuntu 18.04, anacron is now run from systemd.  There are two
systemd units:

/lib/systemd/system/anacron.service
/lib/systemd/system/anacron.timer

The main unit that actually runs anacron is anacron.service.  The
anacron.service unit is run when the PC starts up (as long as mains
power is available) and when it wakes up from a sleep mode.  The
anacron.timer unit runs anacron.service every hour, and
anacron.service runs anacron.  Here is what is in those two unit
files:

root at mypvr:/lib/systemd/system# cat anacron.service
[Unit]
Description=Run anacron jobs
After=time-sync.target
ConditionACPower=true
Documentation=man:anacron man:anacrontab

[Service]
ExecStart=/usr/sbin/anacron -dsq
IgnoreSIGPIPE=false

[Install]
WantedBy=multi-user.target
root at mypvr:/lib/systemd/system# cat anacron.timer
[Unit]
Description=Trigger anacron every hour

[Timer]
OnCalendar=hourly
RandomizedDelaySec=5m
Persistent=true

[Install]
WantedBy=timers.target

So in 18.04, you will get the cron.{daily,weekly,monthly} jobs being
run about 5 minutes after the PC starts up, and after that at about 5
past midnight.  The 5 minutes bit is because after anacron it started,
it wait 5 minutes before it does anything.  That is very useful as it
allows you to kill the anacron task immediately after you reboot your
MythTV box, so it will then run anacron at the usual time instead of
immediately.  You only need to kill anacron if the day has changed
since anacron was last run, as anacron uses timestamps stored in files
in /var/spool/anacron to tell it when its jobs were last run and will
not run them again on the same day (or week or month).  The time that
anacron gets run at has a variable extra delay of up to 5 minutes
because of the "RandomizedDelaySec=5m" line in anacron.timer.  So
anacron will run its tasks 5 minutes after boot, and 5-10 minutes
after the hour after the day changes ie 5-10 minutes after midnight.

In earlier Ubuntu versions, before anacron was run from systemd, it
was run from cron using the file /etc/cron.d/anacron.  That started
anacron at 07:30.  Now, the /etc/cron.d/anacron file will only run
anacron if systemd is not being used.

I found the change in timing from 07:30 to midnight to be a big
problem.  I have a huge database, and my backup and database check
jobs take over half an hour, during which mythfrontend is not very
usable for long periods.  And if I have more than one recording
happening, I can get bad recordings.  Since I often have multiple
recordings happening at midnight, and I am also likely to be watching
a programme, it was very annoying to have anacron running then.  So I
have changed anacron back to being run at 07:30 only.  I consider that
anacron being run every hour is actually a bug - it does not run the
cron.hourly jobs, so it only needs to be run once a day.

To change it back to how it used to be, I created a systemd override
file for anacron.timer:

root at mypvr:/etc/systemd/system# ll -d ana*
drwxr-xr-x 2 root root 4096 Oct 21 01:13 anacron.timer.d/
root at mypvr:/etc/systemd/system# cd anacron.timer.d/
root at mypvr:/etc/systemd/system/anacron.timer.d# ll
total 12
drwxr-xr-x  2 root root 4096 Oct 21 01:13 ./
drwxr-xr-x 27 root root 4096 Oct 23 23:45 ../
-rw-r--r--  1 root root  166 Oct 21 01:13 anacron-timer-override.conf
root at mypvr:/etc/systemd/system/anacron.timer.d# cat
anacron-timer-override.conf
[Unit]
Description=Trigger anacron at 07:30, as happened before the Ubuntu
18.04 upgrade.

[Timer]
OnCalendar=
OnCalendar=07:30
RandomizedDelaySec=0s
Persistent=true

If you want to create an override file like mine, the easy way is to
do this command:

sudo systemctl edit anacron.timer

and paste my override file into it.  The systemctl edit command is
only available in newer versions of systemd, but it is very useful as
it sets up the override directory and .conf file with the right
ownership and permissions automatically.

I have filed a bug report about this problem, but I have not had any
response to it yet:

https://bugs.launchpad.net/ubuntu/+source/anacron/+bug/1799361