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

[Jim Abernathy]

On 11/6/18 7:46 AM, Stephen Worthington wrote:
> 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


This is a great explanation and very helpful.  I've duplicated what you 
did and will look for the changes to take affect tomorrow.

Thanks,

Jim A