If you are using a LUN to boot from SAN, you need to ensure the changes in your configuration files are applied upon rebooting. This is done by rebuilding the initial ramdisk (initrd or initramfs) to include the proper kernel modules, files, and configuration directives after the configuration changes have been made. As the procedure slightly varies depending on the host, we recommend that you refer to your vendor's documentation for the proper procedure.
When rebuilding the initial ramdisk, you will want to confirm that the necessary dependencies are in place before rebooting the host to avoid any errors during boot. Refer to your vendor's documentation for specific commands to confirm this information.
For example, on Citrix XenServer, you can run the following commands and then use the .cmd file to remake the image.
[root@symcert3 ~]# cd /boot
[root@symcert3 boot]# ls
chain.c32 grub initrd-fallback.img menu.c32 vmlinuz-fallback xen-4.4.1-xs90192.map
config-3.10.0+2 initrd-3.10.0+2.img ldlinux.sys System.map-3.10.0+2 xen-4.4.1-xs90192-d.gz xen-debug.gz
extlinux initrd-3.10.0+2.img.cmd mboot.c32 vmlinuz-3.10.0+2 xen-4.4.1-xs90192-d.map xen.gz
extlinux.conf initrd-3.10-xen.img memtest86+-1.65 vmlinuz-3.10-xen xen-4.4.1-xs90192.gz
[root@symcert3 boot]# sh ./initrd-3.10.0+2.img.cmd