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

[Alex Kost]

Ludovic Courtès (2015-11-24 15:48 +0300) wrote:

> Alex Kost <address@hidden> 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.

I don't agree with your points, so it is "No" for me.

>> 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.

Sorry again, but I read: «No, no, we really shouldn't provide "rm"
command, because it can do a big harm!»  If a user just blindly puts
something in his operating-system declaration or runs "rm -rf ~", then
(s)he deserves the harm (s)he gets.

>>> 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.

Thanks for this NixOS info!

> 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 agree that a modular /etc/profile would be great, but only if *any*
part of it can be changed or removed, otherwise this decision will have
the same problem: one day there will appear users who would like to
change the parts that cannot be changed.

But still I prefer to have a straightforward way to set my own
/etc/profile.  Or maybe it would be good to have even a more general
solution: a way to specify any file that goes to "/etc" dir, something
like this:

(operating-system
  ;; ...
  (etc-files
   ("hosts"   (local-file "/home/me/guix/etc/hosts"))
   ("profile" (local-file "/home/me/guix/bash/my-favourite-etc-profile"))
   ("fstab"   (local-file "/home/me/guix/etc/fstab"))))

You will probably consider this decision evil, but for me it's a perfect
solution.  As I see it:

- these 'etc-files' should have a priority over the default generated
  /etc files;

- "guix system" command should report if these files override the
  default ones, and it can even create "/etc/foobar.default" so that a
  user could look at it any time;

- and of course the manual should warn that 'etc-files' is a very
  dangerous option, blah, blah, blah.

The most valuable thing for me is customizability, and I just can't
stand the situation when developers refuse to provide a way to customize
defaults for no reason (or just because it is potentially dangerous).

I don't like the default grub.cfg, but I've never complained about it
because there is "--no-grub" option, so I can install grub on my own and
use my own grub config.  This is great! :-)

The problem with /etc files, is that they can't be edited directly, and
operating-system doesn't provide a way to change any aspect of these
files, so I always find things that I don't like and that can't be
changed.  This is bad! :-(

> I can give it a try if you want.

Sorry, but this is not what I want.  I would like to have a full control
on any aspect of my system.

-- 
Alex