On Mon, Jan 10, 2022 at 12:55:03PM -0500, Stephen Gallagher wrote:
On Mon, Jan 10, 2022 at 12:30 PM Frank Ch. Eigler <fche@xxxxxxxxxx> wrote:
David Cantrell <dcantrell@xxxxxxxxxx> writes:
> Reading comments and talking to people, the long standing understanding of
> /var is still "that's stuff you can rm -rf and the system will still work
> fine". Technically you could remove the RPM database and the system still
> function [...]
Considering that many other valuable mutable state are put under /var
are put there, databases, container images, etc. etc. etc, this
understanding cannot be correct. We could just leave /var alone.
# sudo du -s /var/lib/*
I *think* what David is suggesting here is that while databases and
container images are indeed changeable data that lives in /var (and
are likely VERY important to the user), they are not critical to the
functioning of the operating system itself. The OS will still boot and
you can still log in[1] if /var is wiped clean, though the system will
probably not be doing anything useful at this point. Whereas if the
RPM database is damaged or removed, a core function of the operating
system (installation and updates) will no longer work.
Yes, that is what I was suggesting.
I think there is definite value in considering adding a new location
(though it need not be at the top-level) for data like this.
I'll note that the FHS states the following[2] in regards to /var:
"Everything that once went into /usr that is written to during system
operation (as opposed to installation and software maintenance) must
be in /var."
This exception seems to me to be clearly implying that "installation
and software maintenance" do not need to be in /var (and as CoreOS has
shown, there's value to keeping it somewhere else).
A further quote from the same section of the FHS suggests the use of
/usr/var, which is a location we are not currently using in the Fedora
Project, but seems like it would fit the requirements for both CoreOS
and traditional RPM Fedora. This same hierarchy could be used for
/var/log and /var/lib/libvirt/images as well.
The FHS reasoning ties back to the read-only /usr goal and sharing /usr among
multiple systems, so you wouldn't want host-specifics written in there. I see
that still applying to image-based management of /usr, honestly.
--
David Cantrell <dcantrell@xxxxxxxxxx>
Red Hat, Inc. | Boston, MA | EST5EDT
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