Re: [Fedora-livecd-list] [PATCH] Boot a Live USB device as read-only after persisting some changes.

[fgrose-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org]

From: Frederick Grose <fgrose@sugarlabs.org>

commit a6cd70fc9df2d299ed4f347461c33e4824df62f0
Author: Frederick Grose <fgrose@sugarlabs.org>

    Enable read-only mounting of a persistent home.img filesystem.
    Enable one to call for filesystem checking of home.img before
    mounting on the next boot.

---
 fedora-live-base.ks | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/fedora-live-base.ks b/fedora-live-base.ks
index 6c76e96..0512f67 100644
--- a/fedora-live-base.ks
+++ b/fedora-live-base.ks
@@ -116,9 +116,13 @@ mountPersistentHome() {
   elif [ ! -b "\$homedev" ]; then
     loopdev=\`losetup -f\`
     if [ "\${homedev##/run/initramfs/live}" != "\${homedev}" ]; then
-      action "Remounting live store r/w" mount -o remount,rw /run/initramfs/live
+        if [ "\$liverw" = rw ]; then
+            action "Remounting live store r/w" mount -o remount,rw /run/initramfs/live
+        else
+            opts="-r"
+        fi
     fi
-    losetup \$loopdev \$homedev
+    losetup \$opts \$loopdev \$homedev
     homedev=\$loopdev
   fi
 
@@ -130,6 +134,22 @@ mountPersistentHome() {
     homedev=/dev/mapper/EncHome
   fi
 
+  # If read-only is requested, prepare a non-persistent overlay and snapshot target.
+  if [ "\$opts" = "-r" ]; then
+    dd if=/dev/null of=/run/initramfs/overlayfs/home_overlay bs=1024 count=1 seek=\$((512*1024)) 2> /dev/null
+    HOME_OVERLAY_LOOPDEV=\$(losetup -f)
+    losetup \$HOME_OVERLAY_LOOPDEV /run/initramfs/overlayfs/home_overlay
+    sz=\$(blockdev --getsz \$homedev)
+    echo 0 \$sz snapshot \$homedev \$HOME_OVERLAY_LOOPDEV N 8 | dmsetup create home-rw
+    homedev=/dev/mapper/home-rw
+  fi
+
+  # Check the filesystem, if requested.
+  if [ -e /forcehomefsck ]; then
+    e2fsck -f -y -v \$homedev || e2fsck -f -y \$homedev
+    rm /forcehomefsck
+  fi
+
   # and finally do the mount
   mount \$mountopts \$homedev /home
   # if we have /home under what's passed for persistent home, then
-- 
1.8.3.1

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