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Chapter 25. Configuring an Installed Linux on System z Instance

For more information about Linux on System z, see the publications listed in Chapter 27, IBM System z References. Some of the most common tasks are described here.

25.1. Adding DASDs
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This section explains how to set a Direct Access Storage Device (DASD) online, format it, and how to make sure it is attached to the system persistently, making it automatically available after a reboot.

Note

Make sure the device is attached or linked to the Linux system if running under z/VM. 
CP ATTACH EB1C TO *
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To link a mini disk to which you have access, issue, for example: 
CP LINK RHEL6X 4B2E 4B2E MR
DASD 4B2E LINKED R/W
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See z/VM: CP Commands and Utilities Reference, SC24-6175 for details about these commands.

25.1.1. Dynamically Setting DASDs Online
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The following procedure describes bringing a DASD online dynamically (not persistently). This is the first step when configuring a new DASD; later procedures will explain how to make it available persistently.

Procedure 25.1. Adding DASD Disks on IBM System z Using the VMCP Driver

  1. Enable the VMCP driver: 
    # modprobe vmcp
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  2. Use the cio_ignore command to remove the DASD from the list of ignored devices and make it visible to Linux: 
    # cio_ignore -r DeviceNumber
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    Replace DeviceNumber with the device number of the DASD. For example: 
    # cio_ignore -r 0102
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  3. Link the disk to the virtual machine: 
    # vmcp 'link * DeviceNumber DeviceNumber rw'
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    Replace DeviceNumber with the device number of the DASD.
  4. Set the device online. Use a command of the following form: 
    # # chccwdev -e DeviceNumber
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    Replace DeviceNumber with the device number of the DASD.
  5. Verify that the disk is ready using the lsdasd command: 
    # lsdasd
Bus-ID     Status      Name      Device  Type  BlkSz  Size      Blocks
==============================================================================
0.0.0100   active      dasda     94:0    ECKD  4096   2347MB    600840
0.0.0301   active      dasdb     94:4    FBA   512    512MB     1048576
0.0.0300   active      dasdc     94:8    FBA   512    256MB     524288
0.0.0101   active      dasdd     94:12   ECKD  4096   2347MB    600840
0.0.0200   active      dasde     94:16   ECKD  4096   781MB     200160
0.0.0102   active      dasdf     94:20   ECKD  4096   2347MB    600840
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    In the above example, device 0102 (shown as 0.0.0102 in the Bus-ID column) is being accessed as /dev/dasdf.
If you followed the above procedure, the new DASD is attached for the current session only. This means that the DASD will not still be attached after you reboot the system. See Section 25.1.2, “Persistently setting DASDs online” for information about attaching the storage device permanently.
You can also find more information in the DASD Chapter in Linux on System z Device Drivers, Features, and Commands on Red Hat Enterprise Linux 6.

25.1.2. Persistently setting DASDs online
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The instructions in Section 25.1.1, “Dynamically Setting DASDs Online” described how to activate DASDs dynamically in a running system. Such changes are not persistent; the DASDs will not be attached after the system reboots. Procedures described in this section assume that you have already attached the DASD dynamically.
Making changes to the DASD configuration persistent in your Linux system depends on whether the DASDs belong to the root (/) file system. Those DASDs required for the root file system need to be activated early during the boot process by the initramfs to be able to mount the root file system. The DASDs which are not part of the root file system can be activated later, simplifying the configuration process.
The list of ignored devices (cio_ignore) is handled transparently for persistent device configurations. You do not need to free devices from the ignore list manually.
If you are attaching a new DASD as part of the root file system, you will have to edit the zipl boot loader's configuration and then regenerate the initramfs so that your changes will take effect after the next reboot. The following procedure explains the steps you need to take.

Procedure 25.2. Permanently Attaching DASDs as Root Devices

  1. Edit the /etc/dasd.conf configuration file using a plain text editor such as Vim, and append a line to this file with your DASD's configuration. You can use parts of the file that describe previously configured devices for reference. A valid configuration line will look similar to the following: 
    0.0.0102 use_diag=0 readonly=0 erplog=0 failfast=0
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  2. Edit the /etc/zipl.conf configuration file. An example zipl.conf file will look similar to the following: 
    [defaultboot]
default=linux
target=/boot/
[linux]
  image=/boot/vmlinuz-2.6.32-19.el6.s390x
  ramdisk=/boot/initramfs-2.6.32-19.el6.s390x.img
  parameters="root=/dev/mapper/vg_devel1-lv_root rd_DASD=0.0.0200,use_diag=0,readonly=0,erplog=0,failfast=0 rd_DASD=0.0.0207,use_diag=0,readonly=0,erplog=0,failfast=0  rd_LVM_LV=vg_devel1/lv_root rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYTABLE=us cio_ignore=all,!0.0.0009"
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    Note the multiple rd_DASD= options on the parameters= line. You must add the new DASD to this line, using the same syntax - the rd_DASD= keyword, followed by the device ID and a comma-separated list of options. See the dasd= parameter description in the DASD device driver chapter in Linux on System z Device Drivers, Features, and Commands on Red Hat Enterprise Linux 6 for details.
  3. The next step is to rebuild the initrd: 
    # mkinitrd -f /boot/initramfs-2.6.32-71.el6.s390x.img `uname -r`
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  4. Then, rebuild the boot loader configuration using the zipl command. You can use the -V option for more detailed output: 
    # zipl -V
Using config file '/etc/zipl.conf'
Target device information
  Device..........................: 5e:00
  Partition.......................: 5e:01
  Device name.....................: dasda
  DASD device number..............: 0201
  Type............................: disk partition
  Disk layout.....................: ECKD/compatible disk layout
  Geometry - heads................: 15
  Geometry - sectors..............: 12
  Geometry - cylinders............: 3308
  Geometry - start................: 24
  File system block size..........: 4096
  Physical block size.............: 4096
  Device size in physical blocks..: 595416
Building bootmap in '/boot/'
Building menu 'rh-automatic-menu'
Adding #1: IPL section 'linux' (default)
  kernel image......: /boot/vmlinuz-2.6.32-19.el6.s390x
  kernel parmline...: 'root=/dev/mapper/vg_devel1-lv_root rd_DASD=0.0.0200,use_diag=0,readonly=0,erplog=0,failfast=0 rd_DASD=0.0.0207,use_diag=0,readonly=0,erplog=0,failfast=0 rd_LVM_LV=vg_devel1/lv_root rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYTABLE=us cio_ignore=all,!0.0.0009'
  initial ramdisk...: /boot/initramfs-2.6.32-19.el6.s390x.img
  component address:
    kernel image....: 0x00010000-0x00a70fff
    parmline........: 0x00001000-0x00001fff
    initial ramdisk.: 0x02000000-0x022d2fff
    internal loader.: 0x0000a000-0x0000afff
Preparing boot device: dasda (0201).
Preparing boot menu
  Interactive prompt......: enabled
  Menu timeout............: 15 seconds
  Default configuration...: 'linux'
Syncing disks...
Done.
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After completing this procedure, the new DASD is persistently attached and can be used as part of the root file system. However, the root file system still needs to be expanded to the new DASD. If your system uses an LVM logical volume for the root file system, you will also need to expand this volume (and the volume group which contains it) to the new DASD. This can be done using the built-in pvcreate, vgextend and lvextend commands to create a physical volume for LVM, expand the existing volume group and expand the root logical volume, respectively. See Section 25.1.5, “Expanding Existing LVM Volumes to New Storage Devices” for details.
DASDs that are not part of the root file system, that is, data disks, are persistently configured in the file /etc/dasd.conf. It contains one DASD per line. Each line begins with the device bus ID of a DASD. Optionally, each line can continue with options separated by space or tab characters. Options consist of key-value-pairs, where the key and value are separated by an equals sign.
The key corresponds to any valid sysfs attribute a DASD may have. The value will be written to the key's sysfs attribute. Entries in /etc/dasd.conf are activated and configured by udev when a DASD is added to the system. At boot time, all DASDs visible to the system get added and trigger udev.
Example content of /etc/dasd.conf: 
0.0.0207
0.0.0200 use_diag=1 readonly=1
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Modifications of /etc/dasd.conf only become effective after a reboot of the system or after the dynamic addition of a new DASD by changing the system's I/O configuration (that is, the DASD is attached under z/VM). Alternatively, you can trigger the activation of a new entry in /etc/dasd.conf for a DASD which was previously not active, by executing the following commands:

Procedure 25.3. Permanently Attaching DASDs as Non-root Devices

  • Trigger the activation by writing to the uevent attribute of the device: 
    echo add > /sys/bus/ccw/devices/device.bus,ID/uevent
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    For example: 
    echo add > /sys/bus/ccw/devices/0.0.021a/uevent
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The next step after bringing the DASD online is to format it, if you need to do so. The following procedure explains the necessary steps.

Warning

This procedure will wipe all existing data on the disk. Make sure to back up any data you want to keep before proceeding.

Procedure 25.4. Formatting a DASD

  1. Wipe all existing data on the DASD using the dasdfmt command. Replace DeviceNumber with the device number of the DASD. When prompted for confirmation (as shown in the example below), type yes to proceed. 
    # dasdfmt -b 4096 -d cdl -p /dev/disk/by-path/ccw-0.0.DeviceNumber
Drive Geometry: 10017 Cylinders * 15 Heads =  150255 Tracks

I am going to format the device /dev/disk/by-path/ccw-0.0.0102 in the following way:
   Device number of device : 0x4b2e
   Labelling device        : yes
   Disk label              : VOL1
   Disk identifier         : 0X0102
   Extent start (trk no)   : 0
   Extent end (trk no)     : 150254
   Compatible Disk Layout  : yes
   Blocksize               : 4096

--->> ATTENTION! <<---
All data of that device will be lost.
Type "yes" to continue, no will leave the disk untouched: yes
cyl    97 of  3338 |#----------------------------------------------|   2%
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    When the progress bar reaches the end and the format is complete, dasdfmt prints the following output: 
    Rereading the partition table...
Exiting...
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    See the dasdfmt(8) man page for information about the syntax of the dasdfmt command.
  2. Use the fdasd command to write a new Linux-compatible partition table to the DASD. Replace DeviceNumber with the device number of the DASD. 
    # fdasd -a /dev/disk/by-path/ccw-DeviceNumber
auto-creating one partition for the whole disk...
writing volume label...
writing VTOC...
checking !
wrote NATIVE!
rereading partition table...
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    This example uses the -a option to create a single partition spanning the entire disk. Other layouts are possible; up to three partitions can be created on a single DASD. For information about the syntax of the fdasd command and available options, see the fdasd(8) man page.
  3. Create a new partition with fdisk. Replace DeviceName with the device name of the DASD. 
    # fdisk /dev/DeviceName
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    After you execute fdisk, a series of prompts will appear in your terminal. These prompts can be used to manipulate the disk partition table, creating new partitions or editing existing one. For information about using fdisk, see the fdisk(8) man page.
After a (low-level formatted) DASD is online, it can be used like any other disk under Linux. For instance, you can create file systems, LVM physical volumes, or swap space on its partitions, for example /dev/disk/by-path/ccw-0.0.4b2e-part1. Never use the full DASD device (dev/dasdb) for anything but the commands dasdfmt and fdasd. If you want to use the entire DASD, create one partition spanning the entire drive as in the fdasd example above.

Note

To add additional disks later without breaking existing disk entries in, for example, /etc/fstab, use the persistent device symbolic links under /dev/disk/by-path/.
If your system uses LVM, you need to expand an existing volume group and one or more logical volumes so that they contain the new DASD which you attached by following the procedures described earlier in this chapter. Otherwise, the DASD will be attached to the system, but you will not be able to use it.
The following procedure explains how to use the entire capacity of the new DASD to expand an existing logical volume. If you want to use the new DASD for multiple logical volumes, you will need to create multiple LVM physical volumes on this partition, and repeat this procedure for each logical volume (and volume group) you want to expand. This procedure assumes you followed the steps in Section 25.1.1, “Dynamically Setting DASDs Online” to attach the new DASD dynamically, then Section 25.1.2.1, “DASDs Which Are Part of the Root File System” to attach it persistently and prepare it to be used for the root volume, and that you formatted it as described in Section 25.1.4, “Preparing a New DASD with Low-level Formatting” and created a single partition on it.

Procedure 25.5. Expanding Existing Logical Volume to Use a New DASD

  1. Create a new physical volume for LVM on the DASD using the pvcreate command: 
    # pvcreate /dev/DeviceName
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    Important

    The device name must be specified as a partition - for example, /dev/dasdf1. Do not specify the entire block device.
  2. List existing physical volumes using the pvs command to verify that the physical volume has been created: 
    # pvs
PV                 VG             Fmt  Attr PSize   PFree
 /dev/dasda2        vg_local       lvm2 a--    1,29g       0
 /dev/dasdd1        vg_local       lvm2 a--    2,29g       0
 /dev/dasdf1                       lvm2 a--    2,29g    2,29g
 /dev/mapper/mpathb vgextnotshared lvm2 a--  200,00g 1020,00m
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    As you can see in the above example, /dev/dasdf1 now contains an empty physical volume which is not assigned to any volume group.
  3. Use the vgextend command to expand an existing volume group containing the volume you want to use the new DASD for: 
    # vgextend VolumeGroup PhysicalVolume
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    Replace VolumeGroup with the name of the volume group you are expanding, and PhysicalVolume with the name of the physical volume (for example, /dev/dasdf1).
  4. Use the lvextend command to expand a logical volume you want to use the new DASD for: 
    # lvextend -L +Size /dev/mapper/VolumeGroup-LogicalVolume
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    For example: 
    # lvextend -L +2G /dev/mapper/vg_local-lv_root
Extending logical volume lv_root to 2,58 GiB
Logical volume lv_root successfully resized
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After you complete the procedure, an existing logical volume is expanded and contains the new DASD in addition to any previously assigned storage devices. You can also use the pvs, vgs, and lvs commands as root to view existing LVM physical volumes, volume groups and logical volumes at any point during the procedure.
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