42da66ac7b
For squashfs all needed functionality for idmapped mounts is already implemented by the generic handlers in the VFS. Thus, it is sufficient to just enable the corresponding FS_ALLOW_IDMAP flag to support idmapped mounts. We use this for unprivileged (user namespaced) containers based on squashfs images as rootfs in GyroidOS. A simple test using the mount-idmapped tool executed as user with uid=1000 looks as follows: $ mkdir test $ echo "test" > test/test_file $ mksquashfs test/ fs.img $ sudo mkdir /mnt/test $ sudo mkdir /mnt/mapped $ sudo mount fs.img -o loop /mnt/test/ $ sudo ./mount-idmapped --map-mount b:1000:2000:1 /mnt/test/ /mnt/mapped/ $ mount | tail -n2 fs.img on /mnt/test type squashfs (ro,relatime,errors=continue) fs.img on /mnt/mapped type squashfs (ro,relatime,idmapped,errors=continue) $ ls -lan /mnt/test/ total 5 drwxr-xr-x 2 1000 1000 32 Okt 24 13:36 . drwxr-xr-x 6 0 0 4096 Okt 24 13:38 .. -rw-r--r-- 1 1000 1000 5 Okt 24 13:36 test_file $ ls -lan /mnt/mapped/ total 5 drwxr-xr-x 2 2000 2000 32 Okt 24 13:36 . drwxr-xr-x 6 0 0 4096 Okt 24 13:38 .. -rw-r--r-- 1 2000 2000 5 Okt 24 13:36 test_file Signed-off-by: Michael Weiß <michael.weiss@aisec.fraunhofer.de> Reviewed-by: Christian Brauner <brauner@kernel.org> Reviewed-by: Phillip Lougher <phillip@squashfs.org.uk> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.