Set environment variable globally

[Andrew Martin]

----- Original Message -----
> From: "J Fernyhough" <j.fernyhough at gmail.com>
> To: "ubuntu-devel-discuss" <ubuntu-devel-discuss at lists.ubuntu.com>
> Sent: Wednesday, April 5, 2017 2:01:26 PM
> Subject: Re: Set environment variable globally

> On 24/03/17 21:19, Andrew Martin wrote:
>> Hello,
>> 
>> I recently saw this blog post regarding performance when the TZ environment
>> variable is not set:
>> https://blog.packagecloud.io/eng/2017/02/21/set-environment-variable-save-thousands-of-system-calls/
>> 
> 
> There's also a good deal of discussion on the HN thread:
> https://news.ycombinator.com/item?id=13697555

Thanks, I had not seen this!

> 
>> I tried defining TZ in /etc/environment and in /etc/profile.d/test.sh, but I
>> cannot get this environment variable to be available in all cases (e.g. if I
>> just execute bash without --login or if I run the sample c program provided in
>> the above article). How can I make the TZ environment variable defined
>> completely system-wide?
> 
> Before you go too far with that, is there a specific reason you want to
> do this? For example, there's not generally a lot of advantage unless
> you have a process that does a lot of timezone-based processing.
> 
> However, all you should need in /etc/environment is:
> 
> TZ=:/etc/localtime
> 
> or an equivalent TZ value, e.g.:
> 
> TZ=:Europe/London
> 

I've noticed apache2 reading /etc/localtime a lot when running; this is also
mentioned in the HN thread:
http://mail-archives.apache.org/mod_mbox/httpd-dev/201111.mbox/%3CCAMDeyhzRAZ4eyz%3D%2BstA%3DwoTibM-W6QL8TqT%2BaPio07UddCz7Tg%40mail.gmail.com%3E

It seems like that would have some performance impact. Setting TZ in the
/etc/environment file doesn't appear to be used by upstart or systemd, and
therefore apache2 doesn't use it either. How can I make it be used for services
started by either init system?

Thanks,

Andrew