On 4/10/19 12:24 AM, [email protected] wrote: > On 4/9/19 11:58 PM, Ludovic Courtès wrote: >> Hello, >> >> [email protected] skribis: >> >>> On a system I'm porting to guix I have 2GB tmpfs with subdirectories >>> like /tmpfs/etc that I remount to /etc with an overlay filesystem. >>> >>> The current way I do this in systemd is making a service dependency >>> between the /tmpfs and /etc mounts that mkdirs /tmpfs/etc and >>> /tmpfs/etc_work, but AFAICT filesystem definitions in guix can only have >>> filesystem dependencies. >>> >>> Are there any other ways I can do this without copying/pasting/modifying >>> gobs of core guix code into my system definition? Like somehow >>> appending (mkdir /tmpfs/etc) onto the tmpfs filesystem service start >>> procedure or something. >> In Guix /etc is mostly populated by “activation programs”, which are >> generated from your config. So I’m not sure what you describe would >> make much sense. > So if /etc can be read-only and boot I'm probably fine... my experience > with other distros was that some other processes needed to write to it. > Ex: modifying resolv.conf. > >> Now, you could try to add a file system declaration that mounts /etc, >> with (needed-for-boot? #t). > My goal is to have a read-only / mount with the ability for programs to > make temporary modifications for operational purposes when necessary, in > limited scopes (like /etc). Can you elaborate on what you're suggesting > here? Mounting something other than the overlayfs on /etc would hide > the system config files. I might be able to use another mount to create > a pseudo- /tmpfs/etc_work subdirectory but it sounds kind of wormy and > overlayfs requires the upper dir and workdir to be the same filesystem > which I think precludes doing any mounting for those subdirectories. > > Thanks for the suggestions! > So I think the short answer I was looking for is that
1. guix already does something like this - it mounts root read only and overlays a tempfs on top (it's still writable though somehow) 2. guix has a complicated mounting process that isn't amenable to changes like this Since my question about disk-image gets into the root filesystem tree I'll move this discussion there entirely.
