[systemd-devel] Support for unmerged-usr systems will be REMOVED in the second half of 2023

[Luca Boccassi]

On Sat, 5 Nov 2022, 10:53 TJ, <systemd at iam.tj> wrote:

> On 05/11/2022 10:36, Mantas Mikulėnas wrote:
> > On Sat, Nov 5, 2022 at 12:06 PM TJ <systemd at iam.tj> wrote:
> >
> >> Just seen this announcement in the v252 changelog:
> >>
> >> "We intend to remove support for split-usr (/usr mounted separately
> >> during boot) ..."
> >>
> >> How does this align with support for separate /usr/ with dm-verity ?
> >>
> >> For example, this will affect nspawn. See "man 1 systemd-nspawn" and
> >> "--root-hash=" where in respect of /usr/ it says:
> >>
> >> "Note that this configures the root hash for the root file system. Disk
> >> images may also contain separate file systems for the /usr/ hierarchy,
> >> which may be Verity protected as well. The root hash for this protection
> >> may be configured via the "user.verity.usrhash" extended file attribute
> >> or via a .usrhash file adjacent to the disk image, following the same
> >> format and logic as for the root hash for the root file system described
> >> here."
> >>
> >
> > /usr can remain on a separate partition as long as it's mounted *by the
> > initrd* (the same way initrd currently mounts your rootfs), so that by
> the
> > time systemd starts it already has the full filesystem.
>
> How does this work when systemd is used inside the initrd, as
> "recommended" / discussed at, for example "Using systemd inside an initrd"
> :
>
> https://systemd.io/INITRD_INTERFACE/
>
> > What's finally being removed is support for having the rootfs itself
> mount
> > /usr halfway through, which requires many things that normally are on
> > /usr/lib to be split between it and /lib instead (such as on Debian).
> >
> > Using the initrd to mount /usr isn't new.
> > <
> https://web.archive.org/web/20150906203654if_/https://www.gentoo.org/support/news-items/2013-09-27-initramfs-required.html
> >
> >
>
> Does it also affect the command-line options "mount.usr=,
> mount.usrfstype=, mount.usrflags=, usrhash=, systemd.verity_usr_data=,
> systemd.verity_usr_hash=, systemd.verity_usr_options=" as per "man 7
> kernel-command-line" ?
>

No, that is unrelated. This is about the ancient notion (that no initrd
tools support anymore) that you can boot userspace with /bin /lib /sbin and
no /usr, with the latter being set up late at boot. This is what is no
longer going to be supported.

>
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