virt/uml/user_mode_linux_howto_v2.rst

46 QEMU which we will cover later in this document.
110 This will create a 16G disk image. The OS will initially allocate only one
111 block and will allocate more as they are written by UML. As of kernel
114 or by running ``tune2fs -o discard /dev/ubdXX`` will request UML to
122 jfs, etc will work too.
142 will be empty and it needs an entry for the root file system::
146 The image hostname will be set to the same as the host on which you
156 Depending on which one is in use, ``/etc/network/interfaces`` will
282   amount of packets UML will attempt to read or write in a single
291   which is being configured. In most cases it will enable TCP segmentation and
293   and the UML side. The UML kernel will produce warnings if it is not.
302   if a packet will need to be re-encapsulated into for instance VXLAN.
331 This will connect vec0 to tap0 on the host. Tap0 must already exist (for example
424 This will configure an Ethernet over ``GRE`` (aka ``GRETAP`` or
425 ``GREIRB``) tunnel which will connect the UML instance to a ``GRE``
486 This will configure an Ethernet over L2TPv3 fixed tunnel which will
563 This will configure a BESS transport using the unix_src Unix domain
588 It will take most normal linux kernel arguments as command line
589 arguments.  Additionally, it will need some UML specific arguments
598 * ``mem=int[K,M,G]`` - amount of memory. By default bytes. It will
632 If UML is run as "linux" with no extra arguments, it will try to start an
643 Example which will divert console number 1 to stdin/stdout::
656 * The null channel - Discard all input or output. Example ``con=null`` will set
667   will make UML use the host 8th console (usually unused).
688 This will run an instance with ``2048M RAM``, try to use the image file
689 called ``Filesystem.img`` as root. It will connect to the host using tap0.
690 All consoles except ``con1`` will be disabled and console 1 will
696 If you have not set up a password when generating the image, you will have to
735 That file is the socket that uml_mconsole will use to communicate with
864 from a shared disk.  It will result in filesystem corruption.
879 Sharing file system data will also help performance, since the host will
881 so UML disk requests will be served from the host's memory rather than
898 doesn't, the driver will create and initialize it.
903 UML has TRIM support which will release any unused space in its disk
910 Any changes to the master image will invalidate all COW files. If this
911 happens, UML will *NOT* automatically delete any of the COW files and
912 will refuse to boot. In this case the only solution is to either
914 all COW files which will result in their recreation. Any changes in
915 the COW files will be lost.
935 It also has a destructive merge option which will merge the COW file
939 one of them will invalidate all of the others.  However, it is
961 Hostfs without any parameters to the UML Image will allow the image
983 will mount the host's ``/`` on the virtual machine's ``/mnt/host``.
989 will mount the hosts's /home on the virtual machine's /mnt/home.
1024 knowledge, UML will not know about it and its own in-memory cache of
1031 UML at present is strictly uniprocessor. It will, however spin up a
1035 idle, these threads will be migrated to other processors on a SMP host.
1036 This, unfortunately, will usually result in LOWER performance because of
1038 result, UML will usually benefit from being pinned on a single CPU
1042 Similarly, on large multi-node NUMA systems UML will benefit if all of
1043 its memory is allocated from the same NUMA node it will run on. The
1044 OS will *NOT* do that by default. In order to do that, the sysadmin
1047 in the TMP or TEMP environment variables. UML will look at the values
1048 of ``TMPDIR``, ``TMP`` or ``TEMP`` for that. If that fails, it will
1064 Example - want to try how linux will work with 4096 "proper" network
1083 you can always run UML under gdb and there will be a whole section
1136   will execute an ACPI idle).
1138 As you can see UML will generate quite a bit of output even in idle.The output
1145 You can run UML under gdb now, though it will not necessarily agree to
1153 This will STOP the UML instance, so you must enter `cont` at the GDB