Hacker News Reader

Comment by Infernal | Hacker News Reader

I'm downloading the silverblue iso right now to play with this in a VM. It is surprising to me that ostree does not let you do any sort of bind mount or symlink of a non-reserved location like /gnu to some other filesystem, so I'll have a whack at it.

View on HN

So you can create /gnu/store on Silverblue with the commands (as root)

  chattr -i /
  mkdir -p /gnu/store
  chattr +i /

The last command restores the immutable attribute on the root filesystem. I am able to write arbitrary files (e.g. `touch /gnu/store/test`) even with that attribute set, so it isn't inherited by subdirectories (maybe obvious).

Now, persistence of the /gnu/store data could be an issue, I'm not sure, but maybe this gets you started?

EDIT: next step is to get Guix installed and then try to update the system, we shall see how it goes

I just tried doing that to create the bind mount at /gnu/store via fstab, and it disappeared on reboot (and threw me into an emergency console). Removing the fstab line allowed me to boot normally again.

I think the solution will require using systemd to recreate that folder on boot, and do it early enough to not make the system panic like that.

Maybe that's a bad idea, I don't know enough about ostree/silverblue. However, after some more digging it seems like this solution would be preferable to changing the default guix store with a custom build, since doing that means you can't use any of the pre-compiled binary packages from the official guix servers.

So, having removed the immutable attribute from / and run the guix-install.sh script, the first issue I have is that the script thinks the group 'kvm' exists, because 'getent group kvm' returns successfully. However, if you try to create a user and add them to the kvm group, you get an error about the group not existing. Looking at the contents of /etc/group, there are only 5 groups and none of them are 'kvm'. At the very least it seems that the Guix install script is making some assumptions about the system that Silverblue breaks, which does make me wonder a bit about using the two side by side.

Additionally, I have found some posts as far back as 2017 regarding using Guix or Nix on Fedora Atomic Linux or Fedora Container Linux (it seems the Silverblue name is more recent) and the fact that we're still puzzling it out 5 years later without much in the way of documented success does make me question the viability of the idea a bit.

> It is surprising to me that ostree does not let you do any sort of bind mount or symlink of a non-reserved location like /gnu to some other filesystem, so I'll have a whack at it.

...Well, it might. I actually had zero experience with both ostree/silverblue and guix when I tried doing this, and may have made some hasty assumptions.

EDIT: I do know however that guix doesn't work if the store is a symlink. I tried doing that a while back and it didn't work.

Wouldn't that require that the mountpoint exists in the underlying filesystem? That is, you can't create a /gnu directory to mount into if root is read-only

EDIT: Or is the filesystem not literally read-only? Sibling comment seems to imply that it's just chattr +I'd

I just tried it, and the folder created via chattr disappered after rebooting. So it seems like there's more to it.

Reply on news.ycombinator.com