[systemd-devel] Mounting / as writable without in `/etc/fstab`

[Mantas Mikulėnas]

On Mon, Nov 23, 2020 at 5:23 PM Paul Menzel <
pmenzel+systemd-devel at molgen.mpg.de> wrote:

> Dear systemd folks,
>
>
> Is an entry for / in `/etc/fstab` still needed, or is there a systemd
> way of doing it?
>

That *is* the systemd way -- the fstab entry will be read by
systemd-remount-fs(8) and the new mount options applied.


>
> Installing Debian bullseye/testing with the Debian Installer, it creates
> a GPT and `/etc/fstab`. [...]
> Commenting out the entries for `/`, the root partition is mounted as
> read-only.
>
>      $ findmnt /
>      TARGET SOURCE         FSTYPE OPTIONS
>      /      /dev/nvme0n1p2 ext4   ro,relatime
>
> Shouldn’t it be mounted as writable?
>

No, if you had it initially mounted with 'ro' and did not leave any
instructions for remounting, then it won't be remounted...


>
>      $ sudo /lib/systemd/systemd-remount-fs
>      $ findmnt /
>      TARGET SOURCE         FSTYPE OPTIONS
>      /      /dev/nvme0n1p2 ext4   rw,relatime,errors=remount-ro
>
> The log says:
>
>      [    2.320133] systemd[179]:
> /usr/lib/systemd/system-generators/systemd-gpt-auto-generator succeeded.
>
> I can work around it changing `ro` to `rw` on the Linux command line,
> but I thought, it is possible without that.
>

I would say that having the initramfs directly mount the filesystem as rw
is the *preferred method*, not a workaround... Of course it depends on how
your distro's initramfs wants to work, but at least that's what Arch does
-- since fsck is run from the initramfs, there's not much point in later
mounting it ro at all.

-- 
Mantas Mikulėnas
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