I want to set up a script that automatically changes the timezone on a machine (running ubuntu 11.10) and also sets the right values to the debconf database. I've tried the following, but it does not work (at the end, the current timezone remains unchanged, and if I run manually the dpkg-reconfigure tzdata command, the selected values are indeed the old ones):
#!/bin/sh -e echo "tzdata tzdata/Areas select Europe" | debconf-set-selections echo "tzdata tzdata/Zones/Europe select Madrid" | debconf-set-selections echo "tzdata tzdata/Zones/America select " | debconf-set-selections dpkg-reconfigure -f noninteractive tzdata So, by now, I'm doing it messing with the files /etc/localtime and /etc/timezone directly, but I'd rather prefer the dpkg-reconfigure and debconf way.
3 Answers
Simplest way that I know of is:
echo "Europe/Zurich" > /etc/timezone dpkg-reconfigure -f noninteractive tzdata For using debconf, before calling dpkg-reconfigure, you need to also remove /etc/localtime and /etc/timezone. Also beware of possible extra space (as in your question!) which are not benign.
So "debconf way" that works (in Debian Stretch) would be:
echo "tzdata tzdata/Areas select Europe" | debconf-set-selections echo "tzdata tzdata/Zones/Europe select Madrid" | debconf-set-selections rm -f /etc/localtime /etc/timezone dpkg-reconfigure -f noninteractive tzdata The reason is that tzdata config script tries to be smart, and if it was ever configured before or user has manually meddled with timezones, will behave differently.
EXTRA
To debug similar problem yourself, you would first do:
export DEBCONF_DEBUG=developer which would provide following info:
# dpkg-reconfigure -f noninteractive tzdata debconf (developer): starting /var/lib/dpkg/info/tzdata.config reconfigure 2018e-0+deb9u1 debconf (developer): <-- VERSION 2.0 debconf (developer): --> 0 2.0 debconf (developer): <-- CAPB backup debconf (developer): --> 0 multiselect escape debconf (developer): <-- SET tzdata/Areas Etc debconf (developer): --> 0 value set debconf (developer): <-- SET tzdata/Zones/Etc UTC debconf (developer): --> 0 value set debconf (developer): <-- INPUT high tzdata/Areas debconf (developer): --> 30 question skipped debconf (developer): <-- GO debconf (developer): --> 0 ok debconf (developer): <-- GET tzdata/Areas debconf (developer): --> 0 Etc debconf (developer): <-- INPUT high tzdata/Zones/Etc debconf (developer): --> 30 question skipped debconf (developer): <-- GO debconf (developer): --> 0 ok debconf (developer): starting /var/lib/dpkg/info/tzdata.postinst configure 2018e-0+deb9u1 debconf (developer): <-- VERSION 2.0 debconf (developer): --> 0 2.0 debconf (developer): <-- GET tzdata/Areas debconf (developer): --> 0 Etc debconf (developer): <-- GET tzdata/Zones/Etc debconf (developer): --> 0 UTC debconf (developer): <-- STOP which would show you that it forcefully SETs the values before asking the user for them (thus overwriting values you set with debconf-set-selections).
Then you would change shebang in /var/lib/dpkg/info/tzdata.config from #!/bin/shto #!/bin/sh -x, and follow the program flow, where you would see that it does:
+ [ -L /etc/localtime ] + readlink /etc/localtime + TIMEZONE=/usr/share/zoneinfo/Etc/UTC looking at /var/lib/dpkg/info/tzdata.config you will find this:
# If /etc/localtime is a link, update /etc/timezone if [ -L /etc/localtime ] ; then TIMEZONE="$(readlink /etc/localtime)" which explains why @fiction answer works. Also looking in the script more, you would find that @andrekeller answer also works in newer Debian versions if you remove '/etc/localtime'.
Hopefully this debugging help will help you when next version of Debian makes the script even smarter and existing answers became invalid too. More info on debugging debconf can be found in debconf-devel(7)
I just found out that with Debian Stretch (9) you need to also change /etc/localtime, thus something like:
ln -fs /usr/share/zoneinfo/`cat /etc/timezone` /etc/localtime is needed. To amend andrekeller's answer you need:
echo "Europe/Zurich" > /etc/timezone ln -fs /usr/share/zoneinfo/`cat /etc/timezone` /etc/localtime dpkg-reconfigure -f noninteractive tzdata 
