using ddrescue on the root partition - boot with / as read-only

[Vincent Lefevre <vincent@vinc17.net>]

Hi,

I need to use ddrescue on the root partition of my laptop.

So I need to have the root partition mounted in read-only mode.
How can I do that?

Note that "mount -o remount,ro /" gives an error "mount point is busy"
apparently because various log files are open in write mode.

Using the recovery mode via GRUB (which mounts / in read-only mode)
is useless because the system remounts it later as rw.

Or is there a way to force a remount in read-only mode?
(I could probably trigger a disk error to make the kernel remount /
as read-only, but well...)

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)