/var/guix/gcroot/profiles points to non-existing /mnt subdirectory

/var/guix/gcroot/profiles points to non-existing /mnt subdirectory

[Carlos Sánchez de La Lama]

Hi,

In my Guix SD installation, I have the following contents inside
/var/guix/gcroots:

lrwxrwxrwx 1 root root 18 ago 24 16:45 booted-system -> /run/booted-system
lrwxrwxrwx 1 root root 19 ago 24 16:45 current-system -> /run/current-system
lrwxrwxrwx 1 root root 52 ago 24 16:45 grub.cfg -> /gnu/store/rvcr64gcqvay3g68bsrbcp9kahsnh7an-grub.cfg
lrwxrwxrwx 1 root root 22 ago 24 16:44 profiles -> /mnt/var/guix/profiles

However, /mnt/var/guix/profiles does not exist (there is nothing in
/mnt). Shouldn't it point to /var/guix/profiles?

I have tried a fresh installation, closely following instructions in the
manual, and it happens there as well. I am using 0.10 installation USB
image, I don't know if it happens with 0.11.

Can someone explain if this symlink is correct, and what is its purpose
in that case?

Thanks!

Carlos

Re: /var/guix/gcroot/profiles points to non-existing /mnt subdirectory

[Vincent Legoll]

Hi,

> In my Guix SD installation, I have the following contents inside
> /var/guix/gcroots:
>
> lrwxrwxrwx 1 root root 18 ago 24 16:45 booted-system -> /run/booted-system
> lrwxrwxrwx 1 root root 19 ago 24 16:45 current-system -> /run/current-system
> lrwxrwxrwx 1 root root 52 ago 24 16:45 grub.cfg -> /gnu/store/rvcr64gcqvay3g68bsrbcp9kahsnh7an-grub.cfg
> lrwxrwxrwx 1 root root 22 ago 24 16:44 profiles -> /mnt/var/guix/profiles
>
> I have tried a fresh installation, closely following instructions in the
> manual, and it happens there as well. I am using 0.10 installation USB
> image, I don't know if it happens with 0.11.

I'm on 0.11 GuixSD USB install, and I can see the same:

vince@guixsd ~$ l /var/guix/gcroots/profiles
lrwxrwxrwx 1 root root 22 Aug  5 00:29 /var/guix/gcroots/profiles ->
/mnt/var/guix/profiles

-- 
Vincent Legoll

Re: /var/guix/gcroot/profiles points to non-existing /mnt subdirectory

[Ludovic Courtès]

Hello,

csanchezdll@gmail.com (Carlos Sánchez de La Lama) skribis:

> In my Guix SD installation, I have the following contents inside
> /var/guix/gcroots:
>
> lrwxrwxrwx 1 root root 18 ago 24 16:45 booted-system -> /run/booted-system
> lrwxrwxrwx 1 root root 19 ago 24 16:45 current-system -> /run/current-system
> lrwxrwxrwx 1 root root 52 ago 24 16:45 grub.cfg -> /gnu/store/rvcr64gcqvay3g68bsrbcp9kahsnh7an-grub.cfg
> lrwxrwxrwx 1 root root 22 ago 24 16:44 profiles -> /mnt/var/guix/profiles
>
> However, /mnt/var/guix/profiles does not exist (there is nothing in
> /mnt). Shouldn't it point to /var/guix/profiles?

Indeed.  Having a dangling symlink in there does sound scary since this
is the directory that specifies garbage collector (GC) roots.

Fortunately, the GC automatically looks for roots in /var/guix/profiles
as well:

--8<---------------cut here---------------start------------->8---
Roots LocalStore::findRoots()
{
    Roots roots;

    /* Process direct roots in {gcroots,manifests,profiles}. */
    nix::findRoots(*this, settings.nixStateDir + "/" + gcRootsDir, DT_UNKNOWN, roots);
    if (pathExists(settings.nixStateDir + "/manifests"))
        nix::findRoots(*this, settings.nixStateDir + "/manifests", DT_UNKNOWN, roots);
    nix::findRoots(*this, settings.nixStateDir + "/profiles", DT_UNKNOWN, roots);

    return roots;
}
--8<---------------cut here---------------end--------------->8---

… so this dangling symlink is harmless.

Nevertheless, I went ahead and fixed it in commit
334bda9a9e01b73b772b3f30b04abea35e5391f8.  You can fix it manually on
your system, or delete it.

Thanks!

Ludo’.