This patchset is for VFS.

See commit messages for motivation and details.

Askar Safin (2):
  init: ensure that /dev/console is (nearly) always available in
    initramfs
  init: ensure that /dev/null is (nearly) always available in initramfs

 .../filesystems/ramfs-rootfs-initramfs.rst    |  4 +--
 init/do_mounts.c                              | 11 ++++++++
 init/do_mounts.h                              |  2 ++
 init/initramfs.c                              |  2 ++
 init/main.c                                   |  6 +++-
 init/noinitramfs.c                            | 28 +++----------------
 usr/Makefile                                  |  2 +-
 usr/default_cpio_list                         |  6 +---
 8 files changed, 28 insertions(+), 33 deletions(-)


base-commit: 2961f841b025fb234860bac26dfb7fa7cb0fb122 (mainline)
-- 
2.47.3

On 2/19/26 15:03, Askar Safin wrote:
> This patchset is for VFS.
> 
> See commit messages for motivation and details.

FYI I've been using (and occasionally posting) variants of 
https://landley.net/bin/mkroot/0.8.13/linux-patches/0003-Wire-up-CONFIG_DEVTMPFS_MOUNT-to-initramfs.patch 
since 2017.

What needs /dev/null? I haven't encountered that.

The problem with no /dev/console is init launches with no 
stdin/stdout/stderr (which is what happens for static initramfs made 
with normal user mode cpio, no easy way to insert /dev nodes into the 
filesystem you're archiving up and most cpio tools don't offer an easy 
way to hallucinate nodes). The problem with having no stderr when init 
launches is if anything goes wrong you can't get debug messages.

I have a shell script I run as PID 1 that mounts devtmpfs and then 
redirects stdin/out/err ala 
https://codeberg.org/landley/toybox/src/branch/master/mkroot/mkroot.sh#L111 
but THAT's fiddly because when the shell is opening the file it 
_becomes_ stderr (with the script _itself_ usually having been opened as 
stdin because first available filehandle) so the shell needs plumbing to 
dup2() them up to a high filehandle and close the original one and that 
tends not to get regression tested when anything changes because "we ran 
with no stdin/stdout/stderr is not a common case...

Having the kernel auto-mount devtmpfs (which it already has a config 
option for and all my patch does is make it work for initramfs) fixes 
this, because /dev/console is then available before launching /init.

How is manually editing initramfs _less_ awkward that automounting 
devtmpfs when the config symbol requests it?

Rob

On Mon, Feb 23, 2026 at 3:17 AM Rob Landley <rob@landley.net> wrote:
> FYI I've been using (and occasionally posting) variants of
> https://landley.net/bin/mkroot/0.8.13/linux-patches/0003-Wire-up-CONFIG_DEVTMPFS_MOUNT-to-initramfs.patch
> since 2017.

drivers/base/Kconfig says on CONFIG_DEVTMPFS_MOUNT:
> This option does not affect initramfs based booting

So CONFIG_DEVTMPFS_MOUNT works as documented.

(But I am not against your CONFIG_DEVTMPFS_MOUNT approach
if it helps you fix your problem.)

--
Askar Safin

On 2/23/26 14:58, Askar Safin wrote:
> On Mon, Feb 23, 2026 at 3:17 AM Rob Landley <rob@landley.net> wrote:
>> FYI I've been using (and occasionally posting) variants of
>> https://landley.net/bin/mkroot/0.8.13/linux-patches/0003-Wire-up-CONFIG_DEVTMPFS_MOUNT-to-initramfs.patch
>> since 2017.
> 
> drivers/base/Kconfig says on CONFIG_DEVTMPFS_MOUNT:
>> This option does not affect initramfs based booting
> 
> So CONFIG_DEVTMPFS_MOUNT works as documented.

I.E. they added that instead of merging any of my patches. Doubling down 
on "initramfs isn't a REAL root filesystem"...

*shrug*

> (But I am not against your CONFIG_DEVTMPFS_MOUNT approach
> if it helps you fix your problem.)

Oh I've been patching it locally for years. I'm only replying because I 
was cc'd.

Rob

Rob, I kindly ask you to test this solution to your problems:

https://lore.kernel.org/all/CAPnZJGDDonspVK1WxDac2omkLJVX=_1Tybn4ne+sf3KyaAuofA@mail.gmail.com/

-- 
Askar Safin

On 3/6/26 21:22, Askar Safin wrote:
> Rob, I kindly ask you to test this solution to your problems:
> 
> https://lore.kernel.org/all/CAPnZJGDDonspVK1WxDac2omkLJVX=_1Tybn4ne+sf3KyaAuofA@mail.gmail.com/

Your earlier suggestion that at some point they fixed the kernel build 
so I can go "/path/to/dir /path/to/file.txt" (which didn't _used_ to 
work, I tested it way back when) would presumably solve my problem 
without kernel patches.

I just haven't been programming much since Gavin "spyware" Newsom passed 
his stupid "age verification in the OS" bill 
(https://mstdn.jp/@landley/116194386057190345) where every cloud 
instance needs to report an "age" to Palantir, implying I'll have to 
take mkroot down before Jan 1st to avoid $7k/download fines, and I'm 
looking at maybe getting a job in healthcare or something.

Rob

On Tue, Mar 10, 2026 at 3:51 PM Rob Landley <rob@landley.net> wrote:
>
> On 3/6/26 21:22, Askar Safin wrote:
> > Rob, I kindly ask you to test this solution to your problems:
> >
> > https://lore.kernel.org/all/CAPnZJGDDonspVK1WxDac2omkLJVX=_1Tybn4ne+sf3KyaAuofA@mail.gmail.com/
>
> Your earlier suggestion that at some point they fixed the kernel build
> so I can go "/path/to/dir /path/to/file.txt" (which didn't _used_ to
> work, I tested it way back when) would presumably solve my problem
> without kernel patches.

Cool! Please, write me when you actually test this.

-- 
Askar Safin