Re: Adding operating-system field for a custom /etc/profile.

[ludo@gnu.org (Ludovic Courtès)]

Alex Kost <alezost@gmail.com> skribis:

> Ludovic Courtès (2015-11-23 17:31 +0300) wrote:

[...]

>>> Great!  So is it OK to send a patch for adding ‘profile-file’ field?
>>
>> Hmm, I’m not sure if we want to give direct access to /etc/profile like
>> this.
>
> Oh, no!  If there is one person (me) who wants to have a full control on
> his /etc/profile, there may be the others with the same wish.
>
>> The problem is that several things in there are here to make the system
>> work, and to to make it conform to the ‘operating-system’ declaration,
>> such as:
>>
>>
>> export LANG="en_US.utf8"
>> export TZ="Europe/Paris"
>> export TZDIR="/gnu/store/rwvf6xqgsyb8bmpi7rwk9fildnwvzrv5-tzdata-2015c/share/zoneinfo"
>>
>> # Tell 'modprobe' & co. where to look for modules.
>> export LINUX_MODULE_DIRECTORY=/run/booted-system/kernel/lib/modules
>
> Yes, that's why I suggest to add a note to the manual about a danger of
> using this field.
>
>> The risk I see with adding a raw ‘profile-file’ option is that newcomers
>> may end up getting rid of such things without really noticing, and then
>> getting a broken system.
>
> But a newcomer will learn about this option only if (s)he reads the
> manual with the warning I've mentioned.  For me, your phrase sounds
> like: «We will not provide "rm" command, because a newcomer may
> accidentally run "rm -rf ~"».  Please give me an opportunity to shoot
> myself in the foot!
>
> Besides will the system really be broken?

Yes.

> What do you mean?

I can already see the bug reports: “I specified the en_US.utf8 locale in
the declaration, but somehow I end up with the C locale”; “why doesn’t
modprobe find modules?”; “I’m stuck in the GMT timezone”, etc. etc.

And only after 5 messages will we learn that the user wanted to add
*one* line to /etc/profile, did that via the ‘profile-file’ field,
without noticing that this would wipe out all the rest of the useful
stuff from there.

> Even if /etc/profile is empty, the system will boot successfully and a
> user could login, no?

Sure, but merely booting is not sufficient.

>> What about instead giving a way to populate the top and/or bottom of
>> this file?  Controversial parts, if any, could still be turned on and
>> off by adding or removing services that add these lines?
>
> It is better than nothing, but it is not sufficient IMO.  Any part of
> /etc/profile can be controversial (you'll never know what a user would
> like to change), so I think providing an option to change this file
> completely is essential.
>
> But I agree that appending/prepending some lines may also be useful for
> those who like to keep the default /etc/profile and who just want to add
> something to it.

OK.

NixOS apparently takes in approach similar to that:

  https://github.com/NixOS/nixos/blob/master/modules/programs/bash/bash.nix

There’s a bunch of high-level options like ‘shellAliases’, ‘promptInit’,
etc. that get pasted in /etc/profile or /etc/bashrc.  In addition,
/etc/profile sources /etc/profile.local if available, and similarly for
/etc/bashrc.

‘shellInit’ in that file refers to ‘setEnvironment’, as defined here:

  https://github.com/NixOS/nixos/blob/master/modules/programs/environment.nix
  https://github.com/NixOS/nixos/blob/master/modules/config/shells-environment.nix

Interestingly, that part does like ‘guix package --search-paths’ as
suggested at <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=20255#41>,
but does it in Bash and without stat’ing files.


Anyway, I think the way forward is to make /etc/profile modular in
similar fashion.  What about starting with an /etc/profile service that
can receive Bash snippets and paste them in the middle of the file,
right before:

  if [ -n "$BASH_VERSION" -a -f /etc/bashrc ]
  then
    # Load Bash-specific initialization code.
    . /etc/bashrc
  fi

Does that make sense?

I can give it a try if you want.

Thanks,
Ludo’.