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Re: data files in /etc?

Magosányi Árpád <mag@bunuel.tii.matav.hu> writes:

> Hi!
> There are some files in /etc which are actually data files representing
> the state of the system. Like /etc/mtab, /etc/network/ifstate, or

The BTS has several patches for mount that allow /etc/mtab to be a
link to another file. Thats an extension to being a link to
/proc/mounts, which has some drawbacks like breaking loopback mounts.

For the /etc/network/ifstate afaik someone did a rewrite working
differently at some stage and the package was fixed to deal with it
being linked a long time ago.

> /etc/lvmconf/* (it is not even a text file).

That can also be linked to another location.

> These files are written by programs in occasions one cannot with good
> heart call configuration. Isn't it against the policy?

The problem is that those files have always been there (historic
reason) and that they may be needed during boot before any alternative
place is available (practical reason). They can't be in /var/state if
that is not yet mounted, on a network filesystem/device or lvm, and so
on. Check for the discussions about adding /run or /state.

If they bother you and you know certain conditions don't apply to you
(like var being on a network device) they can be linked. Arguments
about the files has repeadatly ended with the compromise to allow them
to be linked somewhere more fitting for the individual system.

> There are practical reasons behind my question:
> -if one uses a configuration management tool (like tla) to track changes
>  in the configuration, one will stumble upon them sooner or later.
> -if one wants to make the boot process unable to modify configuration,
>  they will also be stumbled upon. (And given the fact that mount
>  actually deletes and recreates /etc/mtab, the challenge is...
>  challenging.)

Or when you want a read-only / and /usr filesystem.

Mounting a ramdisk or tmpfs early during boot and linking the files to
there solves that problem. Note that you need the patch for mount
otherwise it will try to create /etc/mtab~ and iirc /etc/mtab.tmp or


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