Recent docker on MacOS does not allow mounting of /etc/localtime

[micheloosterhof]

Instead of mounting the localtime file, pass the TZ variable to Docker. This may work on Linux as well.

                --hostname in-container \
                --rm \
                $(EXTRA_DOCKER_RUN_ARGS) \
                -v $(HOST_DIR):/host:z \
                -v $(DOCKER_VOLUME_HOME):/home/$(shell whoami) \
-               -v /etc/localtime:/etc/localtime:ro \
+                -e TZ=`ls -la /etc/localtime | cut -d/ -f8-9` \
                $(USER_IMG) $(EXEC)

The cut works on my system, but 8-9 is arbitrary, maybe better written in awk as ls -la /etc/localtime | awk -F '/' '{ printf "%s/%s\n", $(NF - 1), $NF }'

[LukeMondy]

Hey, thanks for reporting this! We don't have a lot of OSX computers to test on, so it's nice to get reports.

This is a tough one, since not all Linuxes will follow OSX's behavior with /etc/localtime. For example, while my Debian box shows similar behavior (where /etc/localtime is symlinked to somewhere more descriptive), it is common (I believe) with RedHat to simply copy a timezone in the the /etc/localtime, which would break the awk/cat system. However, I think you're right that using the env TZ variable is better.

I have come up with a very janky solution:

-e TZ="$$( printf Etc/GMT%+d\\n "$$(( -1* $$(echo 0 $$(date +%z) | bc) / 100 ))" )" \

which I believe may work..?

I'd be good to try it on your commandline first:

printf Etc/GMT%+d\\n "$(( -1* $(echo 0 $(date +%z) | bc) / 100 ))"

it should print something like Etc/GMT-10.

I have put it into the Makefile, and it seems to work on my Debian machine.

It's a bit of a hack, relying on the older, but still compatible, versions of timezones. More info here: https://github.com/eggert/tz/blob/master/etcetera The script uses the date program to get the relative difference to GMT (I believe), then parses it through bc to get it to a usable int, then reverses the sign, and divides by 100 :sweat_smile:

Anyway, can you give it a try, and tell me if it works, and if not, what the commandline outputs?

[micheloosterhof]

$ printf Etc/GMT%+d\\n "$(( -1* $(echo 0 $(date +%z) | bc) / 100 ))"
Etc/GMT-8

[micheloosterhof]

This is good, but on changing to or from daylight savings time the docker container will not automatically migrate to this. The impact of this will probably be small.

[LukeMondy]

Sorry for the mega-delay - we have a PR up now, which should fix this issue. Much simpler than the other options I mentioned, so that's a bonus too. Should be merged soon.