bootdevices.rst (5458B)
1 Boot devices on s390x 2 ===================== 3 4 Booting with bootindex parameter 5 -------------------------------- 6 7 For classical mainframe guests (i.e. LPAR or z/VM installations), you always 8 have to explicitly specify the disk where you want to boot from (or "IPL" from, 9 in s390x-speak -- IPL means "Initial Program Load"). In particular, there can 10 also be only one boot device according to the architecture specification, thus 11 specifying multiple boot devices is not possible (yet). 12 13 So for booting an s390x guest in QEMU, you should always mark the 14 device where you want to boot from with the ``bootindex`` property, for 15 example:: 16 17 qemu-system-s390x -drive if=none,id=dr1,file=guest.qcow2 \ 18 -device virtio-blk,drive=dr1,bootindex=1 19 20 For booting from a CD-ROM ISO image (which needs to include El-Torito boot 21 information in order to be bootable), it is recommended to specify a ``scsi-cd`` 22 device, for example like this:: 23 24 qemu-system-s390x -blockdev file,node-name=c1,filename=... \ 25 -device virtio-scsi \ 26 -device scsi-cd,drive=c1,bootindex=1 27 28 Note that you really have to use the ``bootindex`` property to select the 29 boot device. The old-fashioned ``-boot order=...`` command of QEMU (and 30 also ``-boot once=...``) is not supported on s390x. 31 32 33 Booting without bootindex parameter 34 ----------------------------------- 35 36 The QEMU guest firmware (the so-called s390-ccw bios) has also some rudimentary 37 support for scanning through the available block devices. So in case you did 38 not specify a boot device with the ``bootindex`` property, there is still a 39 chance that it finds a bootable device on its own and starts a guest operating 40 system from it. However, this scanning algorithm is still very rough and may 41 be incomplete, so that it might fail to detect a bootable device in many cases. 42 It is really recommended to always specify the boot device with the 43 ``bootindex`` property instead. 44 45 This also means that you should avoid the classical short-cut commands like 46 ``-hda``, ``-cdrom`` or ``-drive if=virtio``, since it is not possible to 47 specify the ``bootindex`` with these commands. Note that the convenience 48 ``-cdrom`` option even does not give you a real (virtio-scsi) CD-ROM device on 49 s390x. Due to technical limitations in the QEMU code base, you will get a 50 virtio-blk device with this parameter instead, which might not be the right 51 device type for installing a Linux distribution via ISO image. It is 52 recommended to specify a CD-ROM device via ``-device scsi-cd`` (as mentioned 53 above) instead. 54 55 56 Selecting kernels with the ``loadparm`` property 57 ------------------------------------------------ 58 59 The ``s390-ccw-virtio`` machine supports the so-called ``loadparm`` parameter 60 which can be used to select the kernel on the disk of the guest that the 61 s390-ccw bios should boot. When starting QEMU, it can be specified like this:: 62 63 qemu-system-s390x -machine s390-ccw-virtio,loadparm=<string> 64 65 The first way to use this parameter is to use the word ``PROMPT`` as the 66 ``<string>`` here. In that case the s390-ccw bios will show a list of 67 installed kernels on the disk of the guest and ask the user to enter a number 68 to chose which kernel should be booted -- similar to what can be achieved by 69 specifying the ``-boot menu=on`` option when starting QEMU. Note that the menu 70 list will only show the names of the installed kernels when using a DASD-like 71 disk image with 4k byte sectors. On normal SCSI-style disks with 512-byte 72 sectors, there is not enough space for the zipl loader on the disk to store 73 the kernel names, so you only get a list without names here. 74 75 The second way to use this parameter is to use a number in the range from 0 76 to 31. The numbers that can be used here correspond to the numbers that are 77 shown when using the ``PROMPT`` option, and the s390-ccw bios will then try 78 to automatically boot the kernel that is associated with the given number. 79 Note that ``0`` can be used to boot the default entry. 80 81 82 Booting from a network device 83 ----------------------------- 84 85 Beside the normal guest firmware (which is loaded from the file ``s390-ccw.img`` 86 in the data directory of QEMU, or via the ``-bios`` option), QEMU ships with 87 a small TFTP network bootloader firmware for virtio-net-ccw devices, too. This 88 firmware is loaded from a file called ``s390-netboot.img`` in the QEMU data 89 directory. In case you want to load it from a different filename instead, 90 you can specify it via the ``-global s390-ipl.netboot_fw=filename`` 91 command line option. 92 93 The ``bootindex`` property is especially important for booting via the network. 94 If you don't specify the ``bootindex`` property here, the network bootloader 95 firmware code won't get loaded into the guest memory so that the network boot 96 will fail. For a successful network boot, try something like this:: 97 98 qemu-system-s390x -netdev user,id=n1,tftp=...,bootfile=... \ 99 -device virtio-net-ccw,netdev=n1,bootindex=1 100 101 The network bootloader firmware also has basic support for pxelinux.cfg-style 102 configuration files. See the `PXELINUX Configuration page 103 <https://wiki.syslinux.org/wiki/index.php?title=PXELINUX#Configuration>`__ 104 for details how to set up the configuration file on your TFTP server. 105 The supported configuration file entries are ``DEFAULT``, ``LABEL``, 106 ``KERNEL``, ``INITRD`` and ``APPEND`` (see the `Syslinux Config file syntax 107 <https://wiki.syslinux.org/wiki/index.php?title=Config>`__ for more 108 information).