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systemd/src/shared/switch-root.h
Lennart Poettering c6c5d20de5 Revert "shutdown: do not umount recursively before MS_MOVE"
This reverts commit 6b219b74de.

This commit doesn't look right to me. We have to unmount everything
recursively *before* we MS_MOVE because the MS_MOVE will not get rid of
it for us, and we simply cannot access these mounts after the MS_MOVE is
complete anymore.

This is a fundamental difference between MS_MOVE and pivot_root(). The
latter repivots the entire mount table getting rid of anything outside
of the new root. MS_MOVE otoh just mounts a bunch of mount points to the
top, leaving in place whatever might be underneath it.

Thus, if we go through the MS_MOVE codepath we must unmount everything
explicitly before doing so because otherwise the mounts will be pinned
forever, but be entirely invisble to userspace.
2023-09-02 19:47:58 +08:00

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include <stdbool.h>
typedef enum SwitchRootFlags {
SWITCH_ROOT_DESTROY_OLD_ROOT = 1 << 0, /* rm -rf old root when switching under the condition
* that it is backed by non-persistent tmpfs/ramfs/… */
SWITCH_ROOT_DONT_SYNC = 1 << 1, /* don't call sync() immediately before switching root */
SWITCH_ROOT_RECURSIVE_RUN = 1 << 2, /* move /run/ with MS_REC from old to new root */
} SwitchRootFlags;
int switch_root(const char *new_root, const char *old_root_after, SwitchRootFlags flags);