User Mode Linux v2.4.20-7um
        available at http://user-mode-linux.sourceforge.net/





--showconfig
    Prints the config file that this UML binary was generated from.





mem=<Amount of desired ram>
    This controls how much "physical" memory the kernel allocates
    for the system. The size is specified as a number followed by
    one of 'k', 'K', 'm', 'M', which have the obvious meanings.
    This is not related to the amount of memory in the physical
    machine. It can be more, and the excess, if it's ever used, will
    just be swapped out.
        Example: mem=64M





iomem=<name>,<file>
    Configure <file> as an IO memory region named <name>.





--version
    Prints the version number of the kernel.





root=<file containing the root fs>
    This is actually used by the generic kernel in exactly the same
    way as in any other kernel. If you configure a number of block
    devices and want to boot off something other than ubd0, you 
    would use something like:
        root=/dev/ubd5





ncpus=<# of desired CPUs>
    This tells an SMP kernel how many virtual processors to start.





mode=tt
    When both CONFIG_MODE_TT and CONFIG_MODE_SKAS are enabled, this option
    forces UML to run in tt (tracing thread) mode.  It is not the default
    because it's slower and less secure than skas mode.





--help
    Prints this message.





umid=<name>
    This is used to assign a unique identity to this UML machine and
    is used for naming the pid file and management console socket.





uml_dir=<directory>
    The location to place the pid and umid files.





initrd=<initrd image>
    This is used to boot UML from an initrd image.  The argument is the
    name of the file containing the image.





gdb-pid=<pid>
    gdb-pid is used to attach an external debugger to UML.  This may be
    an already-running gdb or a debugger-like process like strace.





jail
    Enables the protection of kernel memory from processes.





debug
    Starts up the kernel under the control of gdb. See the 
    kernel debugging tutorial and the debugging session pages
    at http://user-mode-linux.sourceforge.net/ for more information.





debugtrace
    Causes the tracing thread to pause until it is attached by a
    debugger and continued.  This is mostly for debugging crashes
    early during boot, and should be pretty much obsoleted by
    the debug switch.





honeypot
    This makes UML put process stacks in the same location as they are
    on the host, allowing expoits such as stack smashes to work against
    UML.  This implies 'jail'.





hostfs=<root dir>,<flags>,...
    This is used to set hostfs parameters.  The root directory argument
    is used to confine all hostfs mounts to within the specified directory
    tree on the host.  If this isn't specified, then a user inside UML can
    mount anything on the host that's accessible to the user that's running
    it.

    The only flag currently supported is 'append', which specifies that all
    files opened by hostfs will be opened in append mode.





ssl[0-9]*=<channel description>
    Attach a console or serial line to a host channel.  See
    http://user-mode-linux.sourceforge.net/input.html for a complete
    description of this switch.





eth[0-9]+=<transport>,<options>
    Configure a network device.





mconsole=notify:<socket>
    Requests that the mconsole driver send a message to the named Unix
    socket containing the name of the mconsole socket.  This also serves
    to notify outside processes when UML has booted far enough to respond
    to mconsole requests.





fake_ide
    Create ide0 entries that map onto ubd devices.





ubd<n>=<filename>
    This is used to associate a device with a file in the underlying
    filesystem. Usually, there is a filesystem in the file, but 
    that's not required. Swap devices containing swap files can be
    specified like this. Also, a file which doesn't contain a
    filesystem can have its contents read in the virtual 
    machine by running dd on the device. n must be in the range
    0 to 7. Appending an 'r' to the number will cause that device
    to be mounted read-only. For example ubd1r=./ext_fs. Appending
    an 's' (has to be after 'r', if there is one) will cause data
    to be written to disk on the host immediately.





fakehd
    Change the ubd device name to "hd".





xterm=<terminal emulator>,<title switch>,<exec switch>
    Specifies an alternate terminal emulator to use for the debugger,
    consoles, and serial lines when they are attached to the xterm channel.
    The values are the terminal emulator binary, the switch it uses to set
    its title, and the switch it uses to execute a subprocess,
    respectively.  The title switch must have the form '<switch> title',
    not '<switch>=title'.  Similarly, the exec switch must have the form
    '<switch> command arg1 arg2 ...'.

    The default values are 'xterm=x-terminal-emulator,-T,-e'.  Values for gnome-terminal
    are 'xterm=gnome-terminal,-t,-x'.





con[0-9]*=<channel description>
    Attach a console or serial line to a host channel.  See
    http://user-mode-linux.sourceforge.net/input.html for a complete
    description of this switch.