Notes on Linux

Dynamic Link Manager (for Linux®) User Guide
Version
9.0.x
Audience
anonymous
Part Number
MK-92DLM113-64
ft:lastEdition
2025-11-06

  • When installing HDLM, do not configure the setting# that prevents the execution of programs under the /var/tmp directory.

    #

    The noexec option

    If the noexec option is specified for the /var/tmp directory, you can use the mount command to check the settings.

    Examples of executing the commands are as follows:

    # mount
/dev/mapper/vg_uma-lv_rhel73_tmp on /var/tmp type xfs (rw,nosuid,noexec,relatime,attr2,inode64,noquota)
#

    Note that if you configure the setting that prevents the execution of programs under the /var/tmp directory after installation of HDLM is complete, operation of HDLM is not affected.

  • Of the items in the /etc/lvm/lvm.conf file, the description formats described in this manual are supported only for the items listed below. For details about the description format for each item, see the relevant descriptions, such as sections Settings for a multipath boot disk environment, Upgrade installation of HDLM in a boot disk environment, and Notes on using LVM2. Items other than those listed below support only the default values of the OS.

    • filter

    • global_filter

    • types

    • write_cache_state

    • md_component_detection

    • use_lvmetad

    • allow_changes_with_duplicate_pvs

    • multipath_component_detection

    • use_devicesfile

  • HDLM can be installed in or removed from a single-user-mode environment or a multi-user-mode environment.

  • For Oracle Linux 8 Update 4 and Oracle Linux 8.4 Unbreakable Enterprise Kernel, the following log might be output during the installation or uninstallation of HDLM because of a bug in the OS. You can ignore this log.

    KAPL09044-I The remove of HDLM-8.8.1.0.944-1 completed successfully.
/sbin/ldconfig: /etc/ld.so.conf.d/kernel-5.4.17-2102.201.3.el8uek.x86_64.conf:6: hwcap directive ignored

  • For Oracle Linux 8 Update 4 and Oracle Linux 8.4 Unbreakable Enterprise Kernel, the following log might be output during the execution of the dracut command or the dlmbootstart utility. You can ignore this log.

    /sbin/ldconfig: /etc/ld.so.conf.d/kernel-5.4.17-2102.201.3.el8uek.x86_64.conf:6: hwcap directive ignored.

  • Note that, if the /var directory is set up on a different partition than the root directory (/), no logs will be output to the /var/log/messages file until the /var directory has been mounted during the OS start process.

  • If multiple OSs exist on a disk that differs physically or logically within the same host, HDLM can be installed on each OS. Also, if multiple kernels exist on one OS, HDLM can be used only when the kernel installed with HDLM is started.

    Note, however, that if the OS is Red Hat Enterprise Linux 7, 8, or 9, you can use HDLM even if HDLM is not installed in the running kernel. In this case, no settings are required.

  • The Start Multipath button on the web console for Red Hat Enterprise Linux 8 or 9 is used to start the Device-Mapper multipath service, so do not click this button.

    If you want to use HDLM, do not click the Start Multipath button.

  • For Red Hat Enterprise Linux 7, 8, or 9, by separating the LUs managed by HDLM from the LUs managed by Device-Mapper multipath, you can use the Device-Mapper multipath functionality to manage some of the LUs recognized by the host. This does not, however, apply if Device-Mapper multipath is used as a boot disk.

    The following procedure describes how to separate the LUs that are managed by HDLM from the LUs that are managed by Device-Mapper multipath.

For environments where the boot disk is an HDLM device

  1. For blacklist in the /etc/multipath.conf file, specify the HDLM devices and LUs that are not managed by Device-Mapper multipath (LUs managed by HDLM).

    The following is an example how to specify blacklist in the /etc/multipath.conf file.

    This example shows the lines (in a configuration file) that specify, for blacklist, the LU whose WWID is 360060e8010027810049714c100000025 (an LU that is not managed by Device-Mapper multipath) and a regular expression for HDLM devices.

    blacklist {
            wwid 360060e8010027810049714c100000025
            devnode "^sddlm[a-z]*"
}

  2. Incorporate the /etc/multipath.conf file that you changed in step 1 into the initial RAM disk image file.

    The following is an example of how to incorporate the /etc/multipath.conf file into the initial RAM disk image file.

    In this example, the running kernel is 3.10.0-514.el7.x86_64.

    1. If necessary, back up the initial RAM disk image file.

      # /bin/cp -a /boot/initramfs-3.10.0-514.el7.x86_64.img /boot/initramfs-3.10.0-514.el7.x86_64.img_backup

    2. Change hdlm_dracut=n defined in the /etc/opt/DynamicLinkManager/hdlm.conf file to hdlm_dracut=y.

    3. Execute the dracut command.

      # /usr/sbin/dracut --force --add multipath --include /etc/multipath /etc/multipath /boot/initramfs-3.10.0-514.el7.x86_64.img `uname -r`

  3. Restart the host.

    # shutdown -r now

  4. Make sure that the LUs that are not managed by the Device-Mapper multipath are set correctly.

    Use the multipath -l command to make sure that the LU registered for blacklist in step 1 is not managed by the Device-Mapper multipath.

    If the LU registered for blacklist is not displayed in the message output by the multipath -l command, the LU that is not managed by the Device-Mapper multipath is set correctly.

    # /usr/sbin/multipath -l

  5. Exclude the LUs that are not managed by HDLM (LUs managed by the Device-Mapper multipath) from the management target.

    You can check the correspondence between LUs and HDLM devices by using the following command:

    # /opt/DynamicLinkManager/bin/dlnkmgr view -lu

    The following is an example of how to exclude an LU that is not managed by HDLM from the management target.

    In this example, /dev/sddlmab is excluded from the HDLM management target.

    # /sbin/dlmcfgmgr -o /dev/sddlmab

  6. Make sure that the LUs that are not managed by HDLM are set correctly.

    Use the dlmcfgmgr -v command to make sure that the LU excluded from the management target in step 5 is no longer managed by HDLM.

    If the Management status of the LU excluded from the management targets is unconfigured in the message output by the dlmcfgmgr -v command, the LU that is not managed by HDLM is set correctly.

    # /sbin/dlmcfgmgr -v
HDevName        Management      Device     Host    Channel Target  Lun
/dev/sddlmab    unconfigured    /dev/sdc         1       0       0       1

For environments where the boot disk is not an HDLM device

  1. For blacklist in the /etc/multipath.conf file, specify the HDLM devices and LUs that are not managed by the Device-Mapper multipath (LUs managed by HDLM).

    The following is an example how to specify blacklist in the /etc/multipath.conf file.

    This example shows the lines (in a configuration file) that specify, for blacklist, the LU whose WWID is 360060e8010027810049714c100000025 (an LU that is not managed by the Device-Mapper multipath) and a regular expression for HDLM devices.

    blacklist {
            wwid 360060e8010027810049714c100000025
            devnode "^sddlm[a-z]*"
}

  2. If Device-Mapper multipath is incorporated into the initial RAM disk image file, incorporate the file /etc/multipath.conf, that you changed in step 1, into the initial RAM disk image file. If Device-Mapper multipath is not incorporated into the initial RAM disk image file, proceed to step 3.

    In this example, the running kernel is 3.10.0-514.el7.x86_64.

    1. If necessary, back up the initial RAM disk image file.

      # /bin/cp -a /boot/initramfs-3.10.0-514.el7.x86_64.img /boot/initramfs-3.10.0-514.el7.x86_64.img_backup

    2. Execute the dracut command.

      # /usr/sbin/dracut --force --add multipath --include /etc/multipath /etc/multipath /boot/initramfs-3.10.0-514.el7.x86_64.img `uname -r`

  3. Restart the host.

    # shutdown -r now

  4. Make sure that the LUs that are not managed by the Device-Mapper multipath are set correctly.

    Use the multipath -l command to make sure that the LU registered for blacklist in step 1 is not managed by the Device-Mapper multipath.

    If the LU registered for blacklist is not displayed in the message output by the multipath -l command, the LU that is not managed by the Device-Mapper multipath is set correctly.

    # /usr/sbin/multipath -l

  5. Exclude the LUs that are not managed by HDLM (LUs managed by the Device-Mapper multipath) from the management target.

    You can check the correspondence between LUs and HDLM devices by using the following command:

    # /opt/DynamicLinkManager/bin/dlnkmgr view -lu

    The following is an example of how to exclude an LU that is not managed by HDLM from the management target.

    In this example, /dev/sddlmab is excluded from the HDLM management target.

    # /sbin/dlmcfgmgr -o /dev/sddlmab

  6. Make sure that the LUs that are not managed by HDLM are set correctly.

    Use the dlmcfgmgr -v command to make sure that the LU excluded from the management target in step 5 is no longer managed by HDLM.

    If the Management status of the LU excluded from the management targets is unconfigured in the message output by the dlmcfgmgr -v command, the LU that is not managed by HDLM is set correctly.

    # /sbin/dlmcfgmgr -v
HDevName        Management      Device     Host    Channel Target  Lun
/dev/sddlmab    unconfigured    /dev/sdc         1       0       0       1

  • For OSs other than Red Hat Enterprise Linux 7, 8, or 9, you cannot use HDLM along with the Device-Mapper multipath function.

    You can check whether the Device-Mapper multipath function is enabled by checking whether device-mapper-multipath is installed and multipath devices are enabled.

    Disable multipath devices if device-mapper-multipath is installed and if multipath devices are enabled. For details on how to disable multipath devices, see the device-mapper-multipath documentation. The examples below show how to check whether device-mapper-multipath is installed and whether multipath devices are enabled.

    • If multipath devices are enabled:

      # rpm -q device-mapper-multipath
device-mapper-multipath-0.8.4-10.el8.x86_64
#
#  /sbin/multipath -l
mpathe (360060e80089988000050998800000be1) dm-4 HITACHI,OPEN-V
size=2.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 7:0:1:1 sdm 8:192 active undef running
  `- 9:0:1:1 sdi 8:128 active undef running
mpathd (360060e80089988000050998800000be0) dm-3 HITACHI,OPEN-V
size=2.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 7:0:1:0 sdk 8:160 active undef running
  `- 9:0:1:0 sdh 8:112 active undef running
                       :
                       :

    • If multipath devices are disabled:

      If you execute the /sbin/multipath -l command, no information appears.

      # /sbin/multipath -l
#

  • If you use a Hitachi HBA driver (Hitachi FIVE-EX based Fibre Channel to PCIe HBA) in a Red Hat Enterprise Linux 7 environment, create an initial RAM disk image file while the driver is loaded. In addition, if you perform a re-installation or upgrade installation of the Hitachi HBA driver, re-create an initial RAM disk image file.

  • In a QLogic 8400 Series (FCoE) environment, an HDLM device might not be correctly configured when the OS starts.

    If the path status is Online(E) or Offline(E), increase the value of fcoe_boot_delay in the /etc/opt/DynamicLinkManager/hdlm.conf file.

    For fcoe_boot_delay, specify a value (in seconds) from 0 to 86400.

  • In an SAN boot environment that does not use LVM for the boot disk, the following item might be displayed in the menu at startup. After migrating to an HDLM environment, you will not be able to start the device, so do not use it.

    Red Hat Enterprise Linux 9.x (Plow) (on device-name)