reboot syscall can be performed with an additional argument. In some
systems this functionality can be useful to modify the mode of the
next boot performed by the bootloader.
Instead of individually checking for containers in each user do this
once in a new call proc_cmdline() that read the file only if we are not
in a container.
Mounts are "unmounted".
Swaps are "deactivated", not "turned off" nor "disabled".
Loop and DM devices are "detached", not "deleted".
Especially the deleting sounded a bit scary.
In bugreports about hangs during the late shutdown we are often missing
important information - what were we trying to unmount/detach when it hung.
Instead of printing what we successfully unmounted, print what we are
going to unmount/detach. And add messages to mark the completion of
categories (mount/swap/loop/DM).
As it turns out reboot() doesn't actually imply a file system sync, but
only a disk sync. Accordingly, readd explicit sync() invocations
immediately before we invoke reboot().
This is much less dramatic than it might sounds as we umount all
disks/read-only remount them anyway before going down.
The kernel does not allow switching roots if things are mounted
MS_SHARED. As a work-around, remount things MS_PRIVATE before switching
roots.
This should be fixed in the kernel for good.
https://bugzilla.redhat.com/show_bug.cgi?id=847418
Because root is now recursively marked as shared on bootup, we need to
recursively mark root as private. This prevents a pivot_root failure on
shutdown:
Cannot finalize remaining file systems and devices, giving up.
pivot failed: Invalid argument
