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Re: usrmerge -- plan B?




Ian Jackson wrote:
> Unfortunately that means that while a properly planned and executed
> transition to mandatory merged-/usr might well have offered overall
> technical benefits for the Debian ecosystem, this is not now socially
> possible and pressing on is not worth the social costs of being seen
> to bulldoze opposition.

Prematurely declaring victory for an approach you prefer is a more
subtle tactic, but still an unproductive, escalating, and
heat-generating one. There is no such consensus at this time.

Perhaps the correct transition plan is a years-long transition that will
leave Debian unable to avail itself of any of the advantages until done.
Perhaps it isn't. Perhaps there are ways to accomplish that transition
more quickly. Perhaps there are ways we can provide the benefits in the
short term while accomplishing the transition in the long term. But
regardless, please refrain from declaring one of those positions
authoritatively (rather than as your opinion and position) unless that
becomes the consensus.

Nobody here is looking to *bulldoze* opposition. Rather, people are
mostly seeking to *understand* and *address* opposition. There's a big
difference between "this is going to break things" and "here's something
this is going to break, the current solution doesn't address that".  The
latter is a useful contribution; the former without any signs of the
latter is simply FUD. And it's not unreasonable to identify it as such.

For the record, I'm *not* in this mail suggesting a position on whether
the correct solution is to make usrmerge essential. I do think we should
move to moving merged /usr mandatory. Long-term, I *do* think we should
work on making all packages build to install no files to /bin and /lib
and similar, including lintian warnings for installing in / and
eventually autorejects for that. However, I also think it's unreasonable
for that transition to take years; if we can't reasonably accomplish it
in a few months, then 1) we need better mechanisms for distro-wide
changes, and 2) we should consider a solution like usrmerge in the
interim, until we get to the point that no package in the archive
installs to the directories directly in / and we have rejects in place
to prevent any new packages from doing so.

Here's a thought: we already mount /usr at boot time, could we have a
mechanism at boot time that uses some combination of a tmpfs, symlinks,
and mounts to create a /bin that includes individual symlinks to
corresponding binaries in /usr/bin if and *only* if /bin isn't already a
symlink to /usr/bin? That way, /bin on disk doesn't actually contain any
such symlinks, and we don't need an irreversible process like usrmerge.
Keep that up until the transition completes and the last package
transitions, then ship the symlinks in a new base-files and drop the
transitional startup script. Ditto for /sbin and /lib.

We could also have a dh-style script that automatically moves files and
creates a /usr/usrtransition.d/packagename.conf file read by that
boot-time mechanism. Then we know the transition will be handled
correctly, and we won't have packages getting the details wrong and
ending up with RC bugs.

Sound reasonable? I'd be happy to work on that.

- Josh Triplett