I'm wondering who starts unattended-upgrades in my debian-jessie:

  1. my man page

       This program can download and install security  upgrades  automatically
       and  unattended,  taking care to only install packages from the config‐
       ured APT source, and checking for dpkg prompts about configuration file
       changes. All output is logged to /var/log/unattended-upgrades.log.
       This  script  is  the backend for the APT::Periodic::Unattended-Upgrade
       option and designed to be run from cron (e.g. via /etc/cron.daily/apt).
  2. But my crontab doesn't show anything by crontab command:

    @stefano:/etc/cron.daily$ crontab -l
    no crontab for stefano
    # crontab -l
    no crontab for root
  3. But my unattended-upgrade work fine!(my unattended-upgrades log file) :

    2017-02-05 12:42:42,835 INFO Initial blacklisted packages: 
    2017-02-05 12:42:42,866 INFO Initial whitelisted packages: 
    2017-02-05 12:42:42,868 INFO Starting unattended upgrades script
    2017-02-05 12:42:42,870 INFO Allowed origins are: ['o=Debian,n=jessie', 'o=Debian,n=jessie-updates', 'o=Debian,n=jessie-backports', 'origin=Debian,codename=jessie,label=Debian-Security']
    2017-02-05 12:43:15,848 INFO No packages found that can be upgraded unattended

Where do I have to check/modify if I want to change my schedule?

4 Answers 4


With Debian 9 (stretch) and Debian 10 (buster), the schedule of unattended-upgrades is determined in two steps:

  1. The system scheduler (e.g. systemd timers or cron/anacron), and
  2. APT::Periodic intervals.

A lower frequency in one of these will obstruct the higher frequency in the other, so be sure that settings are correct for both steps.

1. The system scheduler

The process is started by the following two systemd timers:

  • apt-daily.timer to update the package lists (apt-get update), and
  • apt-daily-upgrade.timer to install the upgrades (unattended-upgrade).

(The anacron job /etc/cron.daily/apt-compat still exists, but exits if it detects systemd. See other answers or anacron documentation on changing the schedule if you don't use systemd.)

To modify your update schedule:

$ sudo systemctl edit apt-daily.timer

This creates /etc/systemd/system/apt-daily.timer.d/override.conf. Fill it as follows, for example:


Same for the upgrade schedule:

$ sudo systemctl edit apt-daily-upgrade.timer


To check your work:

$ systemctl cat apt-daily{,-upgrade}.timer
$ systemctl --all list-timers apt-daily{,-upgrade}.timer

(Taken partly from Debian Wiki: UnattendedUpgrades.)

2. APT::Periodic intervals

No matter if you use the systemd timers or the anacron job as the system scheduler, both call the same script in the end. That script makes a new, second decision of whether it is time to run again, but now based on the intervals set in APT::Periodic. You should normally find those settings in /etc/apt/apt.conf.d/20auto-upgrades:

APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Unattended-Upgrade "1";

I always thought the "1" value here simply meant True or On, but actually, it is the minimal interval between runs, expressed in days. If the script determines that less time has passed since the last time the requested action was performed, it will simply not perform the action, regardless of the fact that the system scheduler called for it.

With apt versions above 1.5 (Debian 10 buster) you can change the APT::Periodic values from "1" to "always". You do this once and from then on, you only need to interact with the system scheduler (systemd timer or anacron) to change the schedule.

For more details on the above, or if you want to schedule unattended-upgrades to run more than once per day, see my answer here: How to run unattended-upgrades not daily but every few hours.

  • Any chance you can explain what OnCalendar=01:00 means and how I can make it update/upgrade ANY time? Does a single asterisk, like OnCalendar=* work? The linked Debian docs are too limited.
    – NoOne
    Commented Jan 18, 2022 at 21:58
  • 1
    OnCalendar=1:00 means that unattended-upgrades is run every day at 1:00. With OnCalendar=*-*-* *:00:00 you could run unattended-upgrades every hour, for example. Make sure to set the two APT::Periodic options mentioned in Peter's answer to always, so unattended-upgrades performs an upgrade every time it is run.
    – SomeDude
    Commented Mar 19, 2022 at 14:14

Where do I have to check/modify if I want to change my schedule?

The unattended-upgrades is configured to be applied automatically .

To verify it check the /etc/apt/apt.conf.d/20auto-upgrades file , you will get :

APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Unattended-Upgrade "1";

to modify it you should run the following command:

dpkg-reconfigure -plow unattended-upgrades 

sample output:

 Applying updates on a frequent basis is an important part of keeping 
 systems secure. By default, updates need to be applied manually using
 package management tools.

 Alternatively, you can choose to have this system automatically download 
 and install security updates.                                                                   

     Automatically download and install stable updates?

Choose NO to stop the auto update

Verify the /etc/apt/apt.conf.d/20auto-upgrades again, you should get :

APT::Periodic::Update-Package-Lists "0";
APT::Periodic::Unattended-Upgrade "0";


To run the unattended-upgrades weekly edit your /etc/apt/apt.conf.d/20auto-upgrades as follows :

APT::Periodic::Update-Package-Lists "7";
APT::Periodic::Unattended-Upgrade "1";

A detailed example can be found on Debian-Wiki : automatic call via /etc/apt/apt.conf.d/02periodic


This option allows you to specify the frequency (in days) at which the package lists are refreshed. apticron users can do without this variable, since apticron already does this task.

  • If I'd like to set apt-updating weekly and not daily, do I have to change or delete 20auto-upgrades file then type 02periodic file then run/configure something else ? debian web page alternative isn't so much clear about that. Commented Feb 5, 2017 at 16:30
  • OK, but can 02periodic and and 20auto-upgrades files live together? or do I have to delete one? debian web page isn't so much clear about this point. Commented Feb 5, 2017 at 18:10
  • you don't need the 02periodic file because it is an alternative to 20auto-upgrades , you can delete it Or keep it with the same contents of 20auto-upgrades
    – GAD3R
    Commented Feb 5, 2017 at 19:21
  • Is the following procedure correct for disabling all automated updates? reddit.com/r/linuxadmin/comments/kvcfv0/… Commented Jan 12, 2021 at 3:49

/etc/crontab has a run-parts /etc/cron.daily line which references a folder that contains a /etc/cron.daily/apt-compat file which executes exec /usr/lib/apt/apt.systemd.daily


anacron starts unattended-upgrades and other System-cron-jobs.

cat /etc/anacrontab 
# /etc/anacrontab: configuration file for anacron

# See anacron(8) and anacrontab(5) for details.


# These replace cron's entries
1   5   cron.daily  run-parts --report /etc/cron.daily
7   10  cron.weekly run-parts --report /etc/cron.weekly
@monthly    15  cron.monthly    run-parts --report /etc/cron.monthly
  • 1
    But there is no unattended-upgrades reference inside that /etc/anacrontab . How could you tell it runs unattended-upgrades? Commented Oct 12, 2017 at 19:27

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