Why are changes I made to /etc/multipath.conf not taking effect on boot on my boot-from-multipath RHEL system?
Environment
- Red Hat Enterprise Linux 5.5 or later, 6, 7, 8, 9
- device-mapper-multipath
- root (
/
) on a multipath device
Issue
- Settings we've configured in
/etc/multipath.conf
are not taking effect when I boot the system. If I flush my maps and remap the devices with the multipath command after boot, the settings are applied. - We have added multipath entries into
/etc/multipath.conf
to give an alias,UID
andGID
. On boot, the devices are created with the correct alias name, but theUID
andGID
are not set.
Resolution
Important: Ensure that your/etc/fstab
entry has a valid multipath device or UUID of multipath device partition (Example:/dev/mapper/mpathap1
), instead ofUUID
orLABEL
of individual path of multipath device (Example:/dev/sda1
). Otherwise, even if multipath is correctly enabled at boot time, your system will address the individual device instead of multipath device.
Remake the initrd
(RHEL5) / initramfs
(RHEL6, 7, 8 9):
RHEL 5
# mv /boot/initrd-$(uname -r).img /boot/initrd-$(uname -r).img.bak
# mkinitrd /boot/initrd-$(uname -r).img $(uname -r)
RHEL 6, 7, 8, 9
# mv /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.bak
# dracut
Root Cause
When booting from a multipath device (the root file system is on a multipath device), /etc/multipath.conf
is included in the initial ramdisk. As of RHEL 5.5 and later, as well as RHEL 6, 7, 8, 9, the init process in the initrd
or initramfs
will activate all multipath devices using these settings. So, if the initrd
or initramfs
has not been remade after making changes to /etc/multipath.conf
, the old settings will still be used.
Diagnostic Steps
Open the initrd
or initramfs
and look at the version of multipath.conf
it contains, comparing it to the current version in /etc
.
RHEL 5
# zcat initrd-2.6.18-238.1.1.el5.img | cpio -id
# cat ./etc/multipath.conf
RHEL 6, 7, 8, 9
# zcat initramfs-2.6.32-131.17.1.el6.x86_64.img | cpio -id
# cat ./etc/multipath.conf
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