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Old 03-27-2012, 01:48 PM
Michael Mol
Default After /usr conflation: why not copy booting software to /sbin rather than initramfs?

On Tue, Mar 27, 2012 at 9:37 AM, Alan Mackenzie <acm@muc.de> wrote:
> Hello, Gentoo.
> I've been thinking about the problem of the conflation of every
> executable into /usr. *If /usr isn't on /, the system can't boot without
> special preperations. *Nothing new here.
> The method usually discussed is to copy the booting software into an
> initramfs on a partition other than /usr, and use this to mount /usr.
> My question: what, technically, prevents me from copying the booting
> software instead to /sbin and booting the system that way?

Dynamic linking is probably going to be the killer piece. After every
update, you'd need to make sure all the libraries the binary needs are
also accessible on the / mount.

The other piece is probably somewhere along the lines of "if you're
going to use an initramfs anyway, now you can put / on
$composite_block_device, too!" (Which is something I'll probably start
doing on any system where I'd want /usr on a composite block device
anyway. Which is pretty much all of them; I like the load consumer
balancing behaviors I get from RAID{0|5|6})

Old 03-27-2012, 02:19 PM
Michael Mol
Default After /usr conflation: why not copy booting software to /sbin rather than initramfs?

On Tue, Mar 27, 2012 at 10:02 AM, Mike Edenfield <kutulu@kutulu.org> wrote:


> As you move more and more software off of /usr into / you start to realize
> that the idea of "tiny partition that contains just what I need to boot and
> mount /usr" is becoming "not so tiny" anymore. The distinction between what
> is "boot" software versus "user" software gets less clear. Then it's just
> question of how far you take this process before you reach your personal
> threshold of questioning why you have two partitions at all. Whether you
> reach that point or not depends on how complex your boot process is, what
> you actually need running to boot, and how personally invested in a split
> /usr you happen to be

This extends directly by analogy to having binaries on /usr mounted on
anything other than plain disk. Say you wanted to have / on LVM on
RAID6. Now you don't have any choice but to move stuff from /usr/* to
your initramfs, since the kernel isn't even going to automount your
RAID for you if you're not using the 0.9 metadata format, and you've
still got to cope with LVM.

As you say, the boundary between user software and boot software grows
less and less clear, and your *initramfs* grows bigger and bigger. How
long will there remain *any point* to LVM or software RAID, once you
have to preload the bulk of your operating system into RAM before you
can access their contents? One shouldn't need an entire operating
system preloaded into RAM before being able to access the current
versions of anything.

The *real* fun is going to start once you get daemons which happen to
need to be launched while you're still in your initramfs stage, and
then you need to restart those daemons as part of an update later in
the system's uptime. That's going to be a fun one to solve.


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