Re: Remounting tmpfs

[7e9wc56emjakcm@s.rendaw.me]

On 4/9/19 11:58 PM, Ludovic Courtès wrote:
> Hello,
>
> 7e9wc56emjakcm@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.

> 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!