zsh home service breaks guix shell via ssh

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Malte Frank Gerdes
Saku Laesvuori

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Submitted by: Malte Frank Gerdes

Severity: normal

Malte Frank Gerdes wrote on 23 Sep 2023 12:19

Recipients:(address . bug-guix@gnu.org)

Message-ID:868r8xrxu4.fsf@gmail.com

Hi,

i set up a new system last weekend and am connecting to it via ssh. I

also just recently started using guix home.

I noticed that after connecting via ssh the profile that gets created

when doing `guix shell' is not sourced, therefore the environment

variables are not correct. This seems to be because guix home inserts

"[ -n \"$SSH_CLIENT\" ] && source /etc/profile" into the zshenv file. I

assume this is meant to ensure that /etc/profile is sourced because ssh

does not start a login shell? Anyway, removing that line makes

everything work normally. So am i doing it wrong or is this actually

unnecessary?

mfg²

Saku Laesvuori wrote on 24 Sep 2023 17:27

Recipients:(name . Malte Frank Gerdes)(address . malte.f.gerdes@gmail.com)(address . 66168@debbugs.gnu.org)

Message-ID:gvkz2lwzlrs7nokt6fjfy45p4gulpt6xss54dxfvkd7gjmp2tm@jwb7hnnfnj3i

On Sat, Sep 23, 2023 at 12:19:10PM +0200, Malte Frank Gerdes wrote:

Toggle quote (7 lines)

> I noticed that after connecting via ssh the profile that gets created

> when doing `guix shell' is not sourced, therefore the environment

> variables are not correct. This seems to be because guix home inserts

> "[ -n \"$SSH_CLIENT\" ] && source /etc/profile" into the zshenv file. I

> assume this is meant to ensure that /etc/profile is sourced because ssh

> does not start a login shell?

That is correct, it was added in https://issues.guix.gnu.org/64765

because commands like `ssh host -- cmd` (and commands depending on ssh

such as `git pull/push`) failed.

Toggle quote (3 lines)

> Anyway, removing that line makes everything work normally. So am i

> doing it wrong or is this actually unnecessary?

I can reproduce this:

```

$ ssh localhost

$ guix shell gnuplot

$ gnuplot

zsh: command not found: gnuplot

```

However (still within the ssh session)

```

$ guix shell gnuplot -- gnuplot

[gnuplot opens as expected]

```

and weirdly enough

```

$ guix shell --check gnuplot

guix shell: checking the environment variables visible from shell '/gnu/store/i4rj0banq044423if5xwb3df723g14r9-zsh-5.9/bin/zsh'...

guix shell: All is good! The shell gets correct environment variables.

$ gnuplot

zsh: command not found: gnuplot

```

I don't really know what is happening here. Why does it work when

running the command directly and why does `guix shell --check` claim

that everything is correct when clearly something is wrong? If I

understand correctly `.zshenv` should be sourced in all these cases but

for some reason the problems only occur in some of them.

Any ideas?

Malte Frank Gerdes wrote on 24 Sep 2023 20:48

Recipients:(name . Saku Laesvuori)(address . saku@laesvuori.fi)(address . 66168@debbugs.gnu.org)

Message-ID:86cyy75rg1.fsf@gmail.com

Saku Laesvuori <saku@laesvuori.fi> writes:

Toggle quote (12 lines)> [[PGP Signed Part:Undecided]]
> On Sat, Sep 23, 2023 at 12:19:10PM +0200, Malte Frank Gerdes wrote:
>> I noticed that after connecting via ssh the profile that gets created
>> when doing `guix shell' is not sourced, therefore the environment
>> variables are not correct.  This seems to be because guix home inserts
>> "[ -n \"$SSH_CLIENT\" ] && source /etc/profile" into the zshenv file.  I
>> assume this is meant to ensure that /etc/profile is sourced because ssh
>> does not start a login shell?
>
> That is correct, it was added in <https://issues.guix.gnu.org/64765>
> because commands like `ssh host -- cmd` (and commands depending on ssh
> such as `git pull/push`) failed.

Ah, i didn't think about this use case.

Toggle quote (36 lines)>> Anyway, removing that line makes everything work normally.  So am i
>> doing it wrong or is this actually unnecessary?
>
> I can reproduce this:
>
> ```
> $ ssh localhost
> $ guix shell gnuplot
> $ gnuplot
> zsh: command not found: gnuplot
> ```
>
> However (still within the ssh session)
>
> ```
> $ guix shell gnuplot -- gnuplot
> [gnuplot opens as expected]
> ```
>
> and weirdly enough
>
> ```
> $ guix shell --check gnuplot
> guix shell: checking the environment variables visible from shell '/gnu/store/i4rj0banq044423if5xwb3df723g14r9-zsh-5.9/bin/zsh'...
> guix shell: All is good!  The shell gets correct environment variables.
> $ gnuplot
> zsh: command not found: gnuplot
> ```
>
> I don't really know what is happening here. Why does it work when
> running the command directly and why does `guix shell --check` claim
> that everything is correct when clearly something is wrong? If I
> understand correctly `.zshenv` should be sourced in all these cases but
> for some reason the problems only occur in some of them.
>
> Any ideas?

My guess would be that sourcing /etc/profile should only happen once,

but the SSH_CLIENT variable is inherited to the child shell which

evaluates zshenv which in turn sources /etc/profile because SSH_CLIENT

has non-zero length. So /etc/profile is sourced twice.

This is just a wild guess though.

mfg²

Saku Laesvuori wrote on 25 Sep 2023 16:56

Recipients:(name . Malte Frank Gerdes)(address . malte.f.gerdes@gmail.com)(address . 66168@debbugs.gnu.org)

Message-ID:vnlwmxbvzg5gofbvff2tsaefgxx4edsqwzs7vnc3mzqs67fupz@dqbhrbdhs6sk

Toggle quote (39 lines)> > ```
> > $ ssh localhost
> > $ guix shell gnuplot
> > $ gnuplot
> > zsh: command not found: gnuplot
> > ```
> >
> > However (still within the ssh session)
> >
> > ```
> > $ guix shell gnuplot -- gnuplot
> > [gnuplot opens as expected]
> > ```
> >
> > and weirdly enough
> >
> > ```
> > $ guix shell --check gnuplot
> > guix shell: checking the environment variables visible from shell '/gnu/store/i4rj0banq044423if5xwb3df723g14r9-zsh-5.9/bin/zsh'...
> > guix shell: All is good!  The shell gets correct environment variables.
> > $ gnuplot
> > zsh: command not found: gnuplot
> > ```
> >
> > I don't really know what is happening here. Why does it work when
> > running the command directly and why does `guix shell --check` claim
> > that everything is correct when clearly something is wrong? If I
> > understand correctly `.zshenv` should be sourced in all these cases but
> > for some reason the problems only occur in some of them.
> >
> > Any ideas?
>
> My guess would be that sourcing /etc/profile should only happen once,
> but the SSH_CLIENT variable is inherited to the child shell which
> evaluates zshenv which in turn sources /etc/profile because SSH_CLIENT
> has non-zero length.  So /etc/profile is sourced twice.
> 
> This is just a wild guess though.

Seems to be about right. I had just assumed that guix shell would run
the command in a new shell (causing .zshenv to be sourced in all those
cases) but apparently it just calls the command directly. I haven't seen
any problems with sourcing /etc/profile multiple times because it
reloads both system and user profiles, but obviously it doesn't know
about guix shell profiles.

It seems that the default bash configuration only sources /etc/profile
if $SSH_CLIENT is non-empty and bash is used non-interactively.
Something similar could probably be done with zsh, but I would expect it
to still have this issue in certain situation. For example, I think
running a script like this

```
$ ssh host -- guix shell gnuplot <<EOF
...
EOF
```

would probably still fail.

I can't really think of any other possible solution than having an
environment variable that is set by /etc/profile and that makes sourcing
it a no-op.

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