UMLazi FAQ: “mount: special device /proc/mm does not exist.”

UMware DEBUG: Mounting required files and directories in jail.
mount: special device /proc/mm does not exist
UMware ERROR: Unable to mount jail files.

A few people have reported this error message when starting UMLazi guests.

This happens when UMLazi is run on a host without SKAS support. UMLazi 1.0.3.2 expects SKAS support in the host kernel, and throws a fatal error if it doesn’t exist.

Here’s the solution.

SKAS gives you big speed and security advantages when running user-mode linux machines, I highly recommend you compile it into your kernel. Get it at: http://user-mode-linux.sourceforge.net/dl-sf.html

While you’re at it, it’ll make your life a whole lot easier if you compile in:

tmpfs support – CONFIG_TMPFS

Found in File Systems -> Virtual memory file system support

tuntap – CONFIG_TUN

Found Network Device Support -> Universal TUN/TAP device driver support

Filesystems – JFS, Ext2, Ext3, whatever

Any filesystems you want your UML to use should be compiled into the host kernel as well as the guest kernel.

If you can’t install SKAS, or don’t want to, then here are some quick edits that’ll remove the SKAS requirement from UMLazi. In lib_uml, comment out lines 355, 356, 418, 419, and 569, which should match up with these lines below:

lib_uml:355: /bin/umount $UML_JAIL/proc/mm
lib_uml:356: /bin/rm $UML_JAIL/proc/mm
lib_uml:418: /bin/touch $UML_JAIL/proc/mm
lib_uml:419: /bin/mount --bind /proc/mm $UML_JAIL/proc/mm || return 1;
lib_uml:569: /bin/umount $UML_JAIL/proc/mm >/dev/null 2>&1 || return 1;

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