16

I'm trying to use cron to automate my system updates. You can see my crontab, commands, and resulting errors below.

When I run upgrades.sh as root, the script runs fine. When cron runs it, apt-get -y update runs no problem, but aptitude -y safe-upgrade fails. I'm guessing this error: debconf: (This frontend requires a controlling tty.) is because there is a kernel update which in turn updates grub, which requires my explicitly saying it's okay to overwrite /boot/grub/menu.lst. But I don't understand the path errors. And I'd like the updates that don't require my supervision to go through.

I have read through this question and it's as yet unaccepted solution of unattended-upgrades, and I may end up using it, but why can't I use cron? Seems like it should be really simple, and more linuxy.

Crontab

root@daedalus:~/bin# crontab -l
# m h  dom mon dow   command
45 06 * * * ~/bin/upgrades.sh

upgrades.sh

root@daedalus:~/bin# cat upgrades.sh 
#!/bin/bash
/usr/bin/apt-get -y update
/usr/bin/aptitude -y safe-upgrade

Errors

debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
debconf: unable to initialize frontend: Readline
debconf: (This frontend requires a controlling tty.)
debconf: falling back to frontend: Teletype
dpkg-preconfigure: unable to re-open stdin:
Fetched 37.6MB in 4min 23s (143kB/s)
dpkg: warning: 'ldconfig' not found on PATH.
dpkg: warning: 'start-stop-daemon' not found on PATH.
dpkg: warning: 'update-rc.d' not found on PATH.
dpkg: 3 expected program(s) not found on PATH.
NB: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin.
E: Sub-process /usr/bin/dpkg returned an error code (2)
A package failed to install.  Trying to recover:
dpkg: warning: 'ldconfig' not found on PATH.
dpkg: warning: 'start-stop-daemon' not found on PATH.
dpkg: warning: 'update-rc.d' not found on PATH.
dpkg: 3 expected program(s) not found on PATH.
NB: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin.
Reading package lists...
Building dependency tree...
Reading state information...
Reading extended state information...
Initializing package states...
Writing extended state information...
Community
  • 1
djeikyb
  • 32,005

4 Answers4

15

Although your main problem has already been answered, it looks like you're getting debconf warnings because you're running apt-get without an interactive tty. To get rid of these messages, you can set this environment variable:

DEBIAN_FRONTEND=noninteractive
TrinitronX
  • 3,394
10

The messages are telling you that your PATH environment variable is wrong.

Try adding

PATH=/usr/bin:/bin:/usr/sbin:/sbin

to the top of your crontab.

Or you could put the same PATH line as the second line of ~/bin/upgrades.sh. That way your test from the command line and your test from crontab should produce the same results.

Mikel
  • 6,615
1

There is a community wiki page: Reason why crontab does not work. In this case, it seems as though the cause is cron's limited environment variables. Can you run this from a shell script in /etc/cron.daily?

Community
  • 1
0

From CronHowto:

Depending on the commands being run, you may need to expand the root users PATH variable by putting the following line at the top of their crontab file:

PATH=/usr/sbin:/usr/bin:/sbin:/bin

But in fact, everything seems to be fine doing the same as you.... Where did you fetch those errors from?

CRONTAB:

root@PORTATIL:/var/log$ crontab -l
* * */2 * * /usr/share/myupdate.sh > /var/log/myupdate.log

SCRIPT:

root@PORTATIL:/etc# cat /usr/share/myupdate.sh 
#!/bin/bash
#Testing updates
apt-get update -y
apt-get upgrade -y

LOG:

root@PORTATIL:/etc# cat /var/log/myupdate.log 

Hit http://security.ubuntu.com lucid-security Release.gpg
Hit http://archive.canonical.com lucid Release.gpg
Hit http://archive.canonical.com lucid Release.gpg
Hit http://packages.medibuntu.org lucid Release.gpg
Get:1 http://dl.google.com stable Release.gpg [197B]
Hit http://ppa.launchpad.net lucid Release.gpg
Hit http://ppa.launchpad.net lucid Release.gpg
Hit http://ppa.launchpad.net lucid Release.gpg
Hit http://security.ubuntu.com lucid-security Release
Hit http://badgerports.org lucid Release.gpg
Hit http://archive.canonical.com lucid Release
Hit http://ppa.launchpad.net lucid Release.gpg
Hit http://ppa.launchpad.net maverick Release.gpg
Hit http://ppa.launchpad.net lucid Release.gpg
Hit http://ppa.launchpad.net lucid Release.gpg
Hit http://ppa.launchpad.net lucid Release.gpg
Get:2 http://dl.google.com stable Release [1347B]
Hit http://security.ubuntu.com lucid-security/main Packages
Hit http://ppa.launchpad.net lucid Release
Hit http://ppa.launchpad.net lucid Release
Hit http://packages.medibuntu.org lucid Release
Hit http://download.virtualbox.org lucid Release.gpg
Hit http://archive.canonical.com lucid Release
Hit http://linux.dropbox.com lucid Release.gpg
Get:3 http://dl.google.com stable/main Packages [1110B]
Hit http://security.ubuntu.com lucid-security/restricted Packages
Hit http://security.ubuntu.com lucid-security/main Sources
Hit http://security.ubuntu.com lucid-security/restricted Sources
Hit http://security.ubuntu.com lucid-security/universe Packages
Hit http://security.ubuntu.com lucid-security/universe Sources
Hit http://ppa.launchpad.net lucid Release
Hit http://ppa.launchpad.net lucid Release
Hit http://ppa.launchpad.net maverick Release
Hit http://ppa.launchpad.net lucid Release
Hit http://ppa.launchpad.net lucid Release
Hit http://badgerports.org lucid Release
Hit http://archive.canonical.com lucid/partner Packages
Hit http://security.ubuntu.com lucid-security/multiverse Packages
Hit http://security.ubuntu.com lucid-security/multiverse Sources
Hit http://ppa.launchpad.net lucid Release
Hit http://packages.medibuntu.org lucid/free Packages
Hit http://download.virtualbox.org lucid Release
Hit http://es.archive.ubuntu.com lucid Release.gpg
Hit http://linux.dropbox.com lucid Release
Hit http://archive.canonical.com lucid/partner Packages
Hit http://ppa.launchpad.net lucid/main Packages
Hit http://ppa.launchpad.net lucid/main Packages
Hit http://es.archive.ubuntu.com lucid-updates Release.gpg
Hit http://badgerports.org lucid/main Packages
Hit http://ppa.launchpad.net lucid/main Packages
Hit http://ppa.launchpad.net lucid/main Packages
Hit http://ppa.launchpad.net maverick/main Packages
Hit http://ppa.launchpad.net lucid/main Packages
Hit http://ppa.launchpad.net lucid/main Packages
Hit http://packages.medibuntu.org lucid/non-free Packages
Hit http://linux.dropbox.com lucid/main Packages
Hit http://es.archive.ubuntu.com lucid Release
Hit http://download.virtualbox.org lucid/contrib Packages
Hit http://ppa.launchpad.net lucid/main Packages
Hit http://es.archive.ubuntu.com lucid-updates Release
Hit http://es.archive.ubuntu.com lucid/main Packages
Hit http://es.archive.ubuntu.com lucid/restricted Packages
Hit http://es.archive.ubuntu.com lucid/main Sources
Hit http://es.archive.ubuntu.com lucid/restricted Sources
Hit http://es.archive.ubuntu.com lucid/universe Packages
Hit http://es.archive.ubuntu.com lucid/universe Sources
Hit http://es.archive.ubuntu.com lucid/multiverse Packages
Hit http://es.archive.ubuntu.com lucid/multiverse Sources
Hit http://es.archive.ubuntu.com lucid-updates/main Packages
Hit http://es.archive.ubuntu.com lucid-updates/restricted Packages
Hit http://es.archive.ubuntu.com lucid-updates/main Sources
Hit http://es.archive.ubuntu.com lucid-updates/restricted Sources
Hit http://es.archive.ubuntu.com lucid-updates/universe Packages
Hit http://es.archive.ubuntu.com lucid-updates/universe Sources
Hit http://es.archive.ubuntu.com lucid-updates/multiverse Packages
Hit http://es.archive.ubuntu.com lucid-updates/multiverse Sources
Fetched 2654B in 1s (1628B/s)
Reading package lists...
Reading package lists...
Building dependency tree...
Reading state information...
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
luri
  • 4,132