2.26. mkinitrd

The mkinitrd utility creates file system images for use as initial RAM disk (initrd) images.

When running Red Hat Enterprise Linux 5 with an older kernel in a Microsoft Hyper-V virtualization guest, mkinitrd does not include the Microsoft Hyper-V drivers when asked to generate the initial RAM disk for a Red Hat Enterprise Linux 5.9 kernel or later. This causes a kernel panic when the guest is rebooted with such a kernel as there is no driver available for the storage hosting the guest's root file system. To work around this problem, run the mkinitrd utility with either the --preload option that loads the module before any SCSI modules are loaded, or with the --with option that loads the module after SCSI modules are loaded. For more information, refer to the following Knowledge Base article:
https://access.redhat.com/knowledge/solutions/27421
When using an encrypted device, the following error message may be reported during bootup:
```
insmod: error inserting '/lib/aes_generic.ko': -1 File exists
```
This message can safely be ignored. (BZ#466296)
Installation using a Multiple Device (MD) RAID on top of multipath will result in a machine that cannot boot. Multipath to Storage Area Network (SAN) devices which provide RAID internally are not affected. (BZ#467469)

The following known issue applies to the IBM System z architecture:

When installing Red Hat Enterprise Linux 5, the following errors may be returned in install.log:
```
Installing kernel-2.6.18-158.el5.s390x
cp: cannot stat `/sbin/dmraid.static': No such file or directory
```
This message can be safely ignored.
iSCSI root devices do not function correctly if used over an IPv6 network connection. While the installation will appear to succeed, the system will fail to find the root file system during the first boot. (BZ#529636)