I noticed a weird thing on my Chromebook today. It seems like 3 directories are mounted on the same partition and yet have totally different content. I tried googling the issue, but came up with a loot of people trying to have the same content in all directories.

When I run mount | grep /dev/mmcblk0p1 I get:

/dev/mmcblk0p1 on /mnt/stateful_partition type ext4 (rw,nosuid,nodev,noexec,relatime,commit=600,data=ordered)
/dev/mmcblk0p1 on /home type ext4 (rw,nosuid,nodev,noexec,relatime,commit=600,data=ordered)
/dev/mmcblk0p1 on /usr/local type ext4 (rw,nodev,relatime,commit=600,data=ordered)

However when I inspect each directory I get this.

For ls /home

chronos  root  user

For ls /usr/local

chronos  root  user

And for ls /mnt/stateful_partition

crouton  dev_image  encrypted  encrypted.block  encrypted.key  home  lost+found  shutdown_stateful_umount_failure  unencrypted

I noticed, that home is actually a directly in /mnt/stateful_partition, but I still don't fully understand it.

Can anyone enlighten me?


The moment I typed the question I figured it out myself. Maybe someone else is curious too.

The output of mount is misleading. The partition is only mounted on /mnt/stateful_partition and /home and /usr/local are not mounted on the same partition, but seem to be mount --bind to the directories dev-image and home in /mnt/stateful_partition.

Follow up: I opened an issue on Github to suggest a modification for this behavior.

Result: As I learned from this conversation the problem was, as so often, between chair and keyboard. mount is not the correct command, if one wishes to see the SOURCE of a directory. It only shows the partition where the data is stored, without structure information.

The solution is to use findmnt instead that prints a a nice tree of directories and their source.

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