At the time of writing (July) I ought to see British Summer Time which is seasonal GMT+1.
rob@graviton ~$ docker run -ti --rm alpine:3.6 date Fri Jul 14 09:18:28 UTC 2017 rob@graviton ~$ docker run -ti --rm ubuntu:xenial date Fri Jul 14 09:18:45 UTC 2017 rob@graviton ~$ docker run -ti --rm debian:stretch date Fri Jul 14 09:20:39 UTC 2017
How to set the timezone?
how about an environment variable?
rob@graviton ~$ docker run -ti --rm -e TZ=Europe/London debian:stretch date Fri Jul 14 10:21:37 BST 2017
Great, that was simple, how about the others.
rob@graviton ~$ docker run -ti --rm -e TZ=Europe/London ubuntu:xenial date Fri Jul 14 09:21:57 Europe 2017
rob@graviton ~$ docker run -ti --rm -e TZ=Europe/London alpine:3.6 date Fri Jul 14 10:14:39 GMT 2017
Bah!
So, Debian (tested with jessie, stretch and 'stable' images only needs the TZ envrionment variable
Both Alpine and Ubuntu require their respective 'tzdata' package to be installed via your Dockerfile. (but tested here just by running the commands on the base image)
rob@graviton ~$ docker run --rm -e TZ=Europe/London alpine sh -c "apk add --no-cache tzdata; date" fetch http://dl-cdn.alpinelinux.org/alpine/v3.6/main/x86_64/APKINDEX.tar.gz fetch http://dl-cdn.alpinelinux.org/alpine/v3.6/community/x86_64/APKINDEX.tar.gz (1/1) Installing tzdata (2017a-r0) Executing busybox-1.26.2-r5.trigger OK: 7 MiB in 12 packages Fri Jul 14 11:23:33 BST 2017
rob@graviton ~$ docker run -ti --rm -e TZ=Europe/London ubuntu:xenial sh -c "apt-get update && apt-get install tzdata && date" ...downloading .... Fetched 24.2 MB in 6s (3797 kB/s) Reading package lists... Done Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: tzdata 0 upgraded, 1 newly installed, 0 to remove and 10 not upgraded. Need to get 168 kB of archives. After this operation, 2864 kB of additional disk space will be used. Get:1 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 tzdata all 2016j-0ubuntu0.16.04 [168 kB] Fetched 168 kB in 0s (1724 kB/s) debconf: delaying package configuration, since apt-utils is not installed Selecting previously unselected package tzdata. (Reading database ... 4764 files and directories currently installed.) Preparing to unpack .../tzdata_2016j-0ubuntu0.16.04_all.deb ... Unpacking tzdata (2016j-0ubuntu0.16.04) ... Setting up tzdata (2016j-0ubuntu0.16.04) ... debconf: unable to initialize frontend: Dialog debconf: (No usable dialog-like program is installed, so the dialog based frontend cannot be used. at /usr/share/perl5/Debconf/FrontEnd/Dialog.pm line 76.) debconf: falling back to frontend: Readline debconf: unable to initialize frontend: Readline debconf: (Can't locate Term/ReadLine.pm in @INC (you may need to install the Term::ReadLine module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.22.1 /usr/local/share/perl/5.22.1 /usr/lib/x86_64-linux-gnu/perl5/5.22 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.22 /usr/share/perl/5.22 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base .) at /usr/share/perl5/Debconf/FrontEnd/Readline.pm line 7.) debconf: falling back to frontend: Teletype Current default time zone: 'Etc/UTC' Local time is now: Fri Jul 14 10:44:21 UTC 2017. Universal Time is now: Fri Jul 14 10:44:21 UTC 2017. Run 'dpkg-reconfigure tzdata' if you wish to change it. Fri Jul 14 11:44:21 BST 2017
Then the big However...
Using the TZ environment variable will probably suffice in most instances, especially when using Docker. It is really a user setting and is described here: http://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
and suggests that it isn't needed if the system has been set up properly.
In docker's single process environment that would probably be OK for most scenarios, but if there's other forked processes that don't take the paren't environment, then these processes will be left with UTC again
So, how to go belt and braces and get the container setup with a system-wide timezone setting?
I'll demo this here with this final command, which runs a new shell for a system user, without the environment of the original login
su - daemon -s /bin/bash -c date
Debian
Debian already has tzdata, so...
rob@graviton ~$ docker run -ti --rm debian:stretch sh -c "ln -nfs /usr/share/zoneinfo/Europe/London /etc/localtime; dpkg-reconfigure -f noninteractive tzdata; su - daemon -s /bin/bash -c date" Current default time zone: 'Europe/London' Local time is now: Fri Jul 14 12:59:51 BST 2017. Universal Time is now: Fri Jul 14 11:59:51 UTC 2017. Fri Jul 14 12:59:51 BST 2017
Ubuntu
rob@graviton ~$ docker run -ti --rm ubuntu:xenial sh -c "apt-get update && apt-get install tzdata && ln -nfs /usr/share/zoneinfo/Europe/London /etc/localtime && dpkg-reconfigure -f noninteractive tzdata && su - daemon -s /bin/bash -c date" ... downloading ... Fetched 24.2 MB in 6s (3779 kB/s) Reading package lists... Done Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: tzdata 0 upgraded, 1 newly installed, 0 to remove and 10 not upgraded. Need to get 168 kB of archives. After this operation, 2864 kB of additional disk space will be used. Get:1 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 tzdata all 2016j-0ubuntu0.16.04 [168 kB] Fetched 168 kB in 0s (1652 kB/s) debconf: delaying package configuration, since apt-utils is not installed Selecting previously unselected package tzdata. (Reading database ... 4764 files and directories currently installed.) Preparing to unpack .../tzdata_2016j-0ubuntu0.16.04_all.deb ... Unpacking tzdata (2016j-0ubuntu0.16.04) ... Setting up tzdata (2016j-0ubuntu0.16.04) ... debconf: unable to initialize frontend: Dialog debconf: (No usable dialog-like program is installed, so the dialog based frontend cannot be used. at /usr/share/perl5/Debconf/FrontEnd/Dialog.pm line 76.) debconf: falling back to frontend: Readline debconf: unable to initialize frontend: Readline debconf: (Can't locate Term/ReadLine.pm in @INC (you may need to install the Term::ReadLine module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.22.1 /usr/local/share/perl/5.22.1 /usr/lib/x86_64-linux-gnu/perl5/5.22 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.22 /usr/share/perl/5.22 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base .) at /usr/share/perl5/Debconf/FrontEnd/Readline.pm line 7.) debconf: falling back to frontend: Teletype Current default time zone: 'Etc/UTC' Local time is now: Fri Jul 14 11:45:02 UTC 2017. Universal Time is now: Fri Jul 14 11:45:02 UTC 2017. Run 'dpkg-reconfigure tzdata' if you wish to change it. Current default time zone: 'Europe/London' Local time is now: Fri Jul 14 12:45:02 BST 2017. Universal Time is now: Fri Jul 14 11:45:02 UTC 2017. Fri Jul 14 12:45:02 BST 2017
Alpine
rob@graviton ~$ docker run --rm alpine sh -c "apk add --no-cache tzdata; cp /usr/share/zoneinfo/Europe/London /etc/localtime; su - daemon -s /bin/sh -c date" fetch http://dl-cdn.alpinelinux.org/alpine/v3.6/main/x86_64/APKINDEX.tar.gz fetch http://dl-cdn.alpinelinux.org/alpine/v3.6/community/x86_64/APKINDEX.tar.gz (1/1) Installing tzdata (2017a-r0) Executing busybox-1.26.2-r5.trigger OK: 7 MiB in 12 packages Fri Jul 14 13:10:09 BST 2017
Note: I've no idea what the /etc/TZ file in alpine is for.
