On 4/18/19 5:31 AM, Ludovic Courtès wrote: > Hi, > > 7e9wc56emja...@s.rendaw.me skribis: > >> On 4/9/19 11:58 PM, Ludovic Courtès wrote: >>> Hello, >>> >>> 7e9wc56emja...@s.rendaw.me 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. > /etc is writable because of things like ‘resolv.conf’. > > /etc consists mostly of immutable files derived directly from your OS > config (/etc/passwd, /etc/hosts, /etc/polkit-1, /etc/pam.d, etc.), along > with files that contains bits of state (/etc/shadow, /etc/resolv.conf.) > > The former are directly managed by Guix, while the latter are either > left as is or touched with care by Guix (/etc/shadow in particular.) > >>> 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. > The overlay makes a lot of sense. This is what ‘guix system vm’ does: > see the #:volatile-root? parameter of ‘raw-initrd’. > > Perhaps you could simply set #:volatile-root? #t in your initrd to > obtain what you want? > > Thanks, > Ludo’.
Thanks, yeah, that sounds exactly like what I want! TBH I think something's going on strange with my threads, perhaps because I messed up the replies -- after much source reading I found volatile-root and asked about it in my disk-image thread. TBH I'm not clear how that would be set in the config to use with disk-image to get a whole system.
