[systemd-devel] [HEADS-UP] systemd and Storage Daemons for the Root File System

[Jan Engelhardt]

On Tuesday 2012-01-10 23:24, Lennart Poettering wrote:
>
>http://www.freedesktop.org/wiki/Software/systemd/RootStorageDaemons
>
>If you are involved with early-boot stuff, like building initrds, or are
>doing storage stuff or are otherwise interested please have a look.
>--------------
>Processes (run by the root user) whose first character of the zeroth command
>line argument is '@' are excluded from the killing spree, much the same way as
>kernel threads are excluded too. [...]
>Note that this functionality is only to be used by programs running from the
>initramfs, and not for programs running from the root file system itself. 

Forcing the use of @ introduces a policy, which should preferably not be 
done. Since programs started from the initrd obviously should be having 
a /proc/*/{cwd,exe} symlinks pointing to the initramfs vfsmount.

If the initramfs vfsmount (rootfs) is mounted and/or moved (pivot_root) 
somewhere into the main root, one can determine the special processes 
simply by looking for that directory prefix on the procfs links.

And /proc/self/mountinfo will tell you where the rootfs is mounted, so 
that you do not have to hardcode the location where it has been pivoted 
to either.