Cron job doesn't run

Question

I have a cron job which should run once a week to update, upgrade and autoclean apt, but it never seems to work, at least not as far as I can tell.

This is apparent because running sudo apt-get upgrade (weeks after the cron job was added) shows there are packages ready to be upgraded.

System info

Linux squire 4.15.0-88-generic #88-Ubuntu SMP Tue Feb 11 20:11:34 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

Cron job

$ sudo crontab -e

0 12 * * 1 apt-get update && apt-get -y upgrade && apt-get -y autoclean

Processes

$ ps -aux | grep cron

root       674  0.0  0.0   4640   768 ?        Ss   Oct14   0:01 /bin/sh /snap/nextcloud/23743/bin/nextcloud-cron
root       757  0.0  0.0  31320  1636 ?        Ss   Jul27   0:17 /usr/sbin/cron -f
squire   22697  0.0  0.0  14428  1000 pts/0    R+   15:25   0:00 grep --color=auto cron

Systemd service

● cron.service - Regular background program processing daemon
   Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2020-07-27 22:15:57 UTC; 2 months 27 days ago
     Docs: man:cron(8)
 Main PID: 757 (cron)
    Tasks: 1 (limit: 2312)
   CGroup: /system.slice/cron.service
           └─757 /usr/sbin/cron -f

Oct 24 14:09:01 squire CRON[15986]: pam_unix(cron:session): session closed for user root
Oct 24 14:17:01 squire CRON[16575]: pam_unix(cron:session): session opened for user root by (uid=0)
Oct 24 14:17:01 squire CRON[16576]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Oct 24 14:17:01 squire CRON[16575]: pam_unix(cron:session): session closed for user root
Oct 24 15:03:01 squire cron[757]: (root) RELOAD (crontabs/root)
Oct 24 15:09:01 squire CRON[21350]: pam_unix(cron:session): session opened for user root by (uid=0)
Oct 24 15:09:01 squire CRON[21350]: pam_unix(cron:session): session closed for user root
Oct 24 15:17:01 squire CRON[22008]: pam_unix(cron:session): session opened for user root by (uid=0)
Oct 24 15:17:01 squire CRON[22009]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Oct 24 15:17:01 squire CRON[22008]: pam_unix(cron:session): session closed for user root

Manual upgrade

$ sudo apt-get update && sudo apt-get upgrade

Hit:1 http://ppa.launchpad.net/certbot/certbot/ubuntu bionic InRelease
Get:2 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Hit:3 https://deb.torproject.org/torproject.org bionic InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu bionic InRelease      
Get:5 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:6 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Fetched 252 kB in 1s (178 kB/s)                               
Reading package lists... Done
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  base-files linux-generic linux-headers-generic linux-image-generic netplan.io python3-parsedatetime ubuntu-server
The following packages will be upgraded:
  cryptsetup cryptsetup-bin libcryptsetup12 libfreetype6
4 upgraded, 0 newly installed, 0 to remove and 7 not upgraded.
Need to get 714 kB of archives.
After this operation, 6,144 B of additional disk space will be used.
Do you want to continue? [Y/n] 

Updated cron job for output test

0 12 * * 1 ( apt-get update && apt-get -y upgrade && apt-get -y autoclean ) >/tmp/apt.cron.log 2>&2

Log from test

Hit:1 http://ppa.launchpad.net/certbot/certbot/ubuntu bionic InRelease
Hit:2 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:3 https://deb.torproject.org/torproject.org bionic InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Hit:5 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:6 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease
Reading package lists...
Reading package lists...
Building dependency tree...
Reading state information...
Calculating upgrade...
The following packages have been kept back:
  base-files linux-generic linux-headers-generic linux-image-generic
  netplan.io python3-parsedatetime ubuntu-server
The following packages will be upgraded:
  cryptsetup cryptsetup-bin libcryptsetup12 libfreetype6
4 upgraded, 0 newly installed, 0 to remove and 7 not upgraded.
Need to get 714 kB of archives.
After this operation, 6,144 B of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu bionic-updates/main amd64 libcryptsetup12 amd64 2:2.0.2-1ubuntu1.2 [134 kB]
Get:2 http://us.archive.ubuntu.com/ubuntu bionic-updates/main amd64 cryptsetup-bin amd64 2:2.0.2-1ubuntu1.2 [93.0 kB]
Get:3 http://us.archive.ubuntu.com/ubuntu bionic-updates/main amd64 cryptsetup amd64 2:2.0.2-1ubuntu1.2 [152 kB]
Get:4 http://us.archive.ubuntu.com/ubuntu bionic-updates/main amd64 libfreetype6 amd64 2.8.1-2ubuntu2.1 [335 kB]
Fetched 714 kB in 1s (997 kB/s)
dpkg: warning: 'ldconfig' not found in PATH or not executable
dpkg: warning: 'start-stop-daemon' not found in PATH or not executable
dpkg: error: 2 expected programs not found in PATH or not executable
Note: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin

Answer 1

I've just seen your error messages from the log run

dpkg: warning: 'ldconfig' not found in PATH or not executable
dpkg: warning: 'start-stop-daemon' not found in PATH or not executable
dpkg: error: 2 expected programs not found in PATH or not executable

and

Note: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin

Somewhere near the top - above your job definitions - should be one or two lines line these

SHELL=/bin/bash
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin

You don't actually need the SHELL line but since most other things on a Linux-based system tend to run with bash I'd recommend it.

If you don't have anything of yours in /usr/local you can strip the PATH line I've given you right back to just the first four directories. But by default cron's PATH doesn't include the two sbin directories which is why it's erroring with commands not being found.