--- Begin Message ---
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Subject: |
Re: branch master updated: services: nix: Mount Nix store read only. |
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Date: |
Mon, 03 Jun 2024 22:34:35 -0400 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) |
Hello,
guix-commits@gnu.org writes:
> services: nix: Mount Nix store read only.
>
> * gnu/services/nix.scm (nix-shepherd-service): Add requirements.
> (%nix-store-directory): New variable.
> (nix-service-type): Add file-system-service-type extension.
>
> Change-Id: I18a5d58c92c1f2b5b6dcecc3d5b439cc15bf4e49
This commit unfortunately appears to introduce a regression where
reconfiguring a system with the read-only /nix/store causes the
following error:
--8<---------------cut here---------------start------------->8---
guix system: error: chown: Système de fichiers accessible en lecture seulement
--8<---------------cut here---------------end--------------->8---
With the accompanying strace output:
--8<---------------cut here---------------start------------->8---
20261 close(17) = 0
20261 chown("/nix/store", 0, 981) = -1 EROFS (Système de fichiers
accessible en lecture seulement)
20261 close(13) = 0
20261 write(2, "guix system: \33[1;31merror: \33[0m\33[1mchown\33[0m:
Syst\303\250me de fichiers accessible en lecture seulement\n", 99) = 99
--8<---------------cut here---------------end--------------->8---
Are these chown still useful in the activation snippet?
--8<---------------cut here---------------start------------->8---
(define (nix-activation _)
;; Return the activation gexp.
#~(begin
(use-modules (guix build utils)
(srfi srfi-26))
(for-each (cut mkdir-p <>) '("/nix/store" "/nix/var/log"
"/nix/var/nix/gcroots/per-user"
"/nix/var/nix/profiles/per-user"))
(chown "/nix/store"
(passwd:uid (getpw "root")) (group:gid (getpw "nixbld01")))
(chmod "/nix/store" #o775)
(for-each (cut chmod <> #o777) '("/nix/var/nix/profiles"
"/nix/var/nix/profiles/per-user"))))
--8<---------------cut here---------------end--------------->8---
If they are useful only on the first time, perhaps we could catch the
exceptions for when it runs on an already read-only mounted /nix/store?
--
Thanks,
Maxim
--- End Message ---
--- Begin Message ---
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Subject: |
Re: bug#71352: branch master updated: services: nix: Mount Nix store read only. |
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Date: |
Sun, 23 Jun 2024 22:47:33 -0400 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) |
Hi Oleg,
Maxim Cournoyer <maxim.cournoyer@gmail.com> writes:
> Hi Oleg,
>
> [...]
>
>>> Are these chown still useful in the activation snippet?
>>>
>>> (define (nix-activation _)
>>> ;; Return the activation gexp.
>>> #~(begin
>>> (use-modules (guix build utils)
>>> (srfi srfi-26))
>>> (for-each (cut mkdir-p <>) '("/nix/store" "/nix/var/log"
>>> "/nix/var/nix/gcroots/per-user"
>>> "/nix/var/nix/profiles/per-user"))
>>> (chown "/nix/store"
>>> (passwd:uid (getpw "root")) (group:gid (getpw "nixbld01")))
>>> (chmod "/nix/store" #o775)
>>> (for-each (cut chmod <> #o777) '("/nix/var/nix/profiles"
>>> "/nix/var/nix/profiles/per-user"))))
>>>
>>> If they are useful only on the first time, perhaps we could catch the
>>> exceptions for when it runs on an already read-only mounted /nix/store?
>>
>> Indeed, it is a good idea.
>>
>> A hotfix for the issue was discussed and implemented. It has already
>> been pushed to the master branch. The fix involves a simple
>> 'file-exists?' check. You can find more details in the discussion at
>> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=71320
>>
>> What do you think is preferable in this scenario – catching exceptions
>> or sticking with '(unless (file-exists? ...))'? Your thoughts on the
>> best approach here?
>
> Exceptions are usually better than 'check then do' as they avoid the
> TOCTTOU (time-of-check to time-of-use) class of bugs/vulnerabilities.
I'm closing this for now; I'm satisfied that working order has been
restored :-).
--
Thanks,
Maxim
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