Timezone on remote server

There is a well-established idea that servers don’t have a timezone. They all are UTC. Period.

But… When you log in, you want to see a reasonable time. Yes, you can see current time and do some estimations, but it’s tedious. Today I realized, that GNU C library had provided us with a solution.

1. Keep servers at UTC. They don’t need to think about that madness with repeated 3AM during daytime shifts, or missing hours, or other craziness.
2. There is an environment variable ‘TZ’ which forces most of software, dealing with dates, to use specified timezone.
3. You can pass your environment variable TZ into your ssh session (if your ssh server permits this, and your ssh client does).

Where it’s can be used?

1. dmesg -T start to show your local time. To you only. Other users on the server are unaffected. Unfortunately, -T is very buggy.
2. journalctl does so too. You can see your time in journald logs.

Where it’s useless?

Every text-based log (/var/log/syslog) is keeping original time of the server.

Where it mess things up?

If you start any server-like application from screen, or do any ‘server-wide’ writing, you get timezoned output (at best) or mistimed (at worst, when TZ information is stripped away, but date is in timezone).

How to?

There are two ways. Fist: do it manually every time. I find it’s safer, as it’s opt-in approach. You need to know your timezone. Mine is Asia/Nicosia .

You can find your in output of find /usr/share/zoneinfo . (Keep only last one or two things, f.e. Europe/Ljubljana or Turkey or America/Chicago .

Just type in server prompt (I show example for myself for Cyprus):

Manual mode

export TZ=Asia/Nicosia

And you have time-localized output.

Automatic mode

You need to configure both sides:

server, inside `/etc/ssh/sshd_config`:

AcceptEnv TZ

client, inside ~/.ssh/config, or inside /etc/ssh/ssh_config

Host *
  SendEnv TZ

You need to find existing section, if present, or create a new one.

After that you can confirm, that all servers (which accepts TZ variable) shows your local timezone

date
Tue 20 Jul 2021 01:13:47 PM EEST
journalctl |tail -1
Jul 20 13:18:14 trafi sshd[4948]: Disconnected from invalid user admin 91.241.19.42 port 21157 [preauth]

I wanted to show dmesg -T, but it’s buggy beyond timzone things.