From 83260f65f3f02aab620d218860d0d8118e92f257 Mon Sep 17 00:00:00 2001
From: Valentin David <valentin.david@canonical.com>
Date: Tue, 8 Nov 2022 13:13:04 +0100
Subject: [PATCH] Fix mount propagation

To switch root, systemd has to recursively make all mounts private,
then after it recursively make all mounts shared.

However `/run/mnt/*` and `/writable` are used to be bind mounted in
the rest of the file system. For example, there is no reason for mount
`/snap/hello/42` to also show up as
`/writable/system-data/snap/hello/42` and
`/run/mnt/data/system-data/snap/hello/42`.
---
 static/usr/lib/core/remount-core-fs           | 19 +++++++++++++++++++
 .../remount-core-fs.service                   |  1 +
 .../systemd/system/remount-core-fs.service    | 16 ++++++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100755 static/usr/lib/core/remount-core-fs
 create mode 120000 static/usr/lib/systemd/system/local-fs.target.wants/remount-core-fs.service
 create mode 100644 static/usr/lib/systemd/system/remount-core-fs.service

diff --git a/static/usr/lib/core/remount-core-fs b/static/usr/lib/core/remount-core-fs
new file mode 100755
index 00000000..ac5ac4aa
--- /dev/null
+++ b/static/usr/lib/core/remount-core-fs
@@ -0,0 +1,19 @@
+#!/bin/bash
+
+FILESYSTEMS=(
+    /run/mnt/base
+    /run/mnt/data
+    /run/mnt/gadget
+    /run/mnt/kernel
+    /run/mnt/snapd
+    /run/mnt/ubuntu-boot
+    /run/mnt/ubuntu-save
+    /run/mnt/ubuntu-seed
+    /writable
+)
+
+for fs in "${FILESYSTEMS[@]}"; do
+    if mountpoint -q "${fs}"; then
+        mount --make-private "${fs}"
+    fi
+done
diff --git a/static/usr/lib/systemd/system/local-fs.target.wants/remount-core-fs.service b/static/usr/lib/systemd/system/local-fs.target.wants/remount-core-fs.service
new file mode 120000
index 00000000..6898efbb
--- /dev/null
+++ b/static/usr/lib/systemd/system/local-fs.target.wants/remount-core-fs.service
@@ -0,0 +1 @@
+../remount-core-fs.service
\ No newline at end of file
diff --git a/static/usr/lib/systemd/system/remount-core-fs.service b/static/usr/lib/systemd/system/remount-core-fs.service
new file mode 100644
index 00000000..ef20cdbf
--- /dev/null
+++ b/static/usr/lib/systemd/system/remount-core-fs.service
@@ -0,0 +1,16 @@
+[Unit]
+Description=Reset propagation of initial mount points
+DefaultDependencies=no
+Before=local-fs-pre.target
+Before=local-fs.target
+Before=shutdown.target
+Wants=local-fs-pre.target
+Conflicts=shutdown.target
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/lib/core/remount-core-fs
+
+[Install]
+WantedBy=local-fs.target