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Tomas Aschan
Asked: 2011-10-24 17:02:49 +0800 CST

"Unknown filesystem unionfs" although all packages and modules are installed

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I'm trying to mount a unionfs file system in fstab (as one of the steps in this guide), with the following line:

unionfs /usr unionfs nodev,noatime,dirs=/.filesystems/usr/overlay=ro:/usr=rw 0 0

I've installed the package unionfs-fuse and added unionfs to /etc/modules, but when trying to mount -a I still get an error saying

mount: unknown file system type: unionfs

What am I doing wrong here?

11.10

2 Answers

  1. Best Answer

    I've solved (or rather worked around) this, by not using unionfs and instead using aufs - another union file system.

    Install the AUFS package and its kernel module from linux-image-extra-virtual: 

    sudo apt-get install aufs-tools linux-image-extra-virtual

    The corresponding row in my fstab now looks like this:

    usr    /usr    aufs    udba=reval,br:/.filesystems/usr/rw:/.filesystems/usr/ro    0   0

    The squashfs is mounted at /.filesystems/usr/ro in the previous line, making this working as a substitute for the troubling steps in the guide I referred to in the OP.

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  2. Create underlying squashfs on loop device through the terminal:

    /.filesystems/usr/usr.sqfs /usr squashfs ro,loop,nodev 0 0

    Create aufs virtual filesystem that allows you to write on it:

    aufs /usr aufs nodev,noatime,dirs=/.filesystems/usr/overlay=rw:/usr=ro 0 0

    Also consider adjusting /etc/sysctl.conf (!) if shutting down your PC takes longer than it should. Decrease the swap - swap turned off below

    vm.swappiness = 0
m.dirty_background_ratio = 20
vm.dirty_expire_centisecs = 0
vm.dirty_ratio = 80
vm.dirty_writeback_centisecs = 0
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