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23.5. Verifying the Initial RAM Disk Image
The job of the initial RAM disk image is to preload the block device modules, such as for IDE, SCSI or RAID, so that the root file system, on which those modules normally reside, can then be accessed and mounted. On Red Hat Enterprise Linux 6 systems, whenever a new kernel is installed using either the Yum, PackageKit, or RPM package manager, the Dracut utility is always called by the installation scripts to create an initramfs (initial RAM disk image).
You can verify that an
initramfs corresponding to your current kernel version exists and is specified correctly in the
grub.conf configuration file by following this procedure:
Procedure 23.1. Verifying the Initial RAM Disk Image
As root, list the contents in the
/boot/ directory and find the kernel (
vmlinuz- ) and
initramfs- with the latest (most recent) version number:
Example 23.1. Ensuring that the kernel and initramfs versions match
we have three kernels installed (or, more correctly, three kernel files are present in
the latest kernel is
initramfs file matching our kernel version,
initramfs-2.6.32-22.el6.x86_64kdump.img, also exists.
/boot/ directory you may find several
initrd- files. These are special files created by the Kdump mechanism for kernel debugging purposes, are not used to boot the system, and can safely be ignored.
(Optional) If your
initramfs- file does not match the version of the latest kernel in
/boot/, or, in certain other situations, you may need to generate an
initramfs file with the Dracut utility. Simply invoking
dracut as root without options causes it to generate an
initramfs file in the
/boot/ directory for the latest kernel present in that directory:
You must use the
--force option if you want
dracut to overwrite an existing
initramfs (for example, if your
initramfs has become corrupt). Otherwise
dracut will refuse to overwrite the existing
Will not override existing initramfs (/boot/initramfs-2.6.32-22.el6.x86_64.img) without --force
You can create an initramfs in the current directory by calling
dracut "initramfs-$(uname -r).img" $(uname -r)
If you need to specify specific kernel modules to be preloaded, add the names of those modules (minus any file name suffixes such as
.ko) inside the parentheses of the
add_dracutmodules=" directive of the
/etc/dracut.conf configuration file. You can list the file contents of an
initramfs image file created by dracut by using the
drwxr-xr-x 23 root root 0 May 3 22:34 .
drwxr-xr-x 2 root root 0 May 3 22:33 proc
-rwxr-xr-x 1 root root 7575 Mar 25 19:53 init
drwxr-xr-x 7 root root 0 May 3 22:34 etc
drwxr-xr-x 2 root root 0 May 3 22:34 etc/modprobe.d
man dracut and
man dracut.conf for more information on options and usage.
configuration file in the
directory to ensure that an
exists for the kernel version you are booting. Refer to Section 23.6, “Verifying the Boot Loader”
for more information.
Verifying the Initial RAM Disk Image and Kernel on IBM eServer System i
On IBM eSeries System i machines, the initial RAM disk and kernel files are combined into a single file, which is created with the
addRamDisk command. This step is performed automatically if the kernel and its associated packages are installed or upgraded from the RPM packages distributed by Red Hat; thus, it does not need to be executed manually. To verify that it was created, use the command
ls -l /boot/ to make sure the
/boot/vmlinitrd- file already exists (the
should match the version of the kernel just installed).