| Boot devices on s390x |
| ===================== |
| |
| Booting with bootindex parameter |
| -------------------------------- |
| |
| For classical mainframe guests (i.e. LPAR or z/VM installations), you always |
| have to explicitly specify the disk where you want to boot from (or "IPL" from, |
| in s390x-speak -- IPL means "Initial Program Load"). In particular, there can |
| also be only one boot device according to the architecture specification, thus |
| specifying multiple boot devices is not possible (yet). |
| |
| So for booting an s390x guest in QEMU, you should always mark the |
| device where you want to boot from with the ``bootindex`` property, for |
| example:: |
| |
| qemu-system-s390x -drive if=none,id=dr1,file=guest.qcow2 \ |
| -device virtio-blk,drive=dr1,bootindex=1 |
| |
| For booting from a CD-ROM ISO image (which needs to include El-Torito boot |
| information in order to be bootable), it is recommended to specify a ``scsi-cd`` |
| device, for example like this:: |
| |
| qemu-system-s390x -blockdev file,node-name=c1,filename=... \ |
| -device virtio-scsi \ |
| -device scsi-cd,drive=c1,bootindex=1 |
| |
| Note that you really have to use the ``bootindex`` property to select the |
| boot device. The old-fashioned ``-boot order=...`` command of QEMU (and |
| also ``-boot once=...``) is not supported on s390x. |
| |
| |
| Booting without bootindex parameter |
| ----------------------------------- |
| |
| The QEMU guest firmware (the so-called s390-ccw bios) has also some rudimentary |
| support for scanning through the available block devices. So in case you did |
| not specify a boot device with the ``bootindex`` property, there is still a |
| chance that it finds a bootable device on its own and starts a guest operating |
| system from it. However, this scanning algorithm is still very rough and may |
| be incomplete, so that it might fail to detect a bootable device in many cases. |
| It is really recommended to always specify the boot device with the |
| ``bootindex`` property instead. |
| |
| This also means that you should avoid the classical short-cut commands like |
| ``-hda``, ``-cdrom`` or ``-drive if=virtio``, since it is not possible to |
| specify the ``bootindex`` with these commands. Note that the convenience |
| ``-cdrom`` option even does not give you a real (virtio-scsi) CD-ROM device on |
| s390x. Due to technical limitations in the QEMU code base, you will get a |
| virtio-blk device with this parameter instead, which might not be the right |
| device type for installing a Linux distribution via ISO image. It is |
| recommended to specify a CD-ROM device via ``-device scsi-cd`` (as mentioned |
| above) instead. |
| |
| |
| Booting from a network device |
| ----------------------------- |
| |
| Beside the normal guest firmware (which is loaded from the file ``s390-ccw.img`` |
| in the data directory of QEMU, or via the ``-bios`` option), QEMU ships with |
| a small TFTP network bootloader firmware for virtio-net-ccw devices, too. This |
| firmware is loaded from a file called ``s390-netboot.img`` in the QEMU data |
| directory. In case you want to load it from a different filename instead, |
| you can specify it via the ``-global s390-ipl.netboot_fw=filename`` |
| command line option. |
| |
| The ``bootindex`` property is especially important for booting via the network. |
| If you don't specify the the ``bootindex`` property here, the network bootloader |
| firmware code won't get loaded into the guest memory so that the network boot |
| will fail. For a successful network boot, try something like this:: |
| |
| qemu-system-s390x -netdev user,id=n1,tftp=...,bootfile=... \ |
| -device virtio-net-ccw,netdev=n1,bootindex=1 |
| |
| The network bootloader firmware also has basic support for pxelinux.cfg-style |
| configuration files. See the `PXELINUX Configuration page |
| <https://wiki.syslinux.org/wiki/index.php?title=PXELINUX#Configuration>`__ |
| for details how to set up the configuration file on your TFTP server. |
| The supported configuration file entries are ``DEFAULT``, ``LABEL``, |
| ``KERNEL``, ``INITRD`` and ``APPEND`` (see the `Syslinux Config file syntax |
| <https://wiki.syslinux.org/wiki/index.php?title=Config>`__ for more |
| information). |