Links
Install
sudo apt-get install squashfs-tools
Usage
mksquashfs --help mksquashfs source... dest [options] [-e list of exclude dirs/files] [-ef exclude_file] # Creating a squashfs file from a directory. mksquashfs <directory> <squashfs_file.squashfs> -info # Mounting it sudo mount -t squashfs <squashfs_file.squashfs> <mount_point> -o loop # Overlaying read only / read write. # See: http://aufs.sourceforge.net/aufs.html#EXAMPLES sudo mount -t aufs -o br:/rw_branch=rw:/ro_branch=ro none /merged_mount_point # Uncompressing unsquashfs -li <squashfs_file.squashfs>
Overlaying read-write directory over a read-only squashfs
/etc/fstab entry
# First mount the squashfs file as readonly <squashfs_file.squashfs> <mount_directory_read_only> squashfs loop,ro 0 0 # Now mount final location with the union (via aufs) # See: http://aufs.sourceforge.net/aufs.html#EXAMPLES none <mount_directory_final> aufs br=<read_write_directory>=rw:<mount_directory_read_only>=ro 0 0 # This is a better way to go as we use rr instead of # ro for the squashfs branch allowing optimization # in aufs (no need of whiteouts, etc since # underlying fs is really ro.) none <mount_directory_final> aufs br=<read_write_directory>=rw:<mount_directory_read_only>=rr 0 0
e.g.
Assume that you have /opt/local/data.squashfs which is a
squashfs compressed file. You want to mount this such that
/opt/local/data displays it's data, but anything written
to it goes into /opt/local/data.read-write. So we mount
the squashfs into /opt/local/data.read-only and then mount
both this and read-write directory onto /opt/local/data.
/opt/local/data.squashfs /opt/local/data.read-only squashfs loop 0 0 none /opt/local/data aufs br=/opt/local/data.read-write=rw:/opt/local/data.read-only=ro 0 0