30.5. Verifying the Initial RAM Disk Image

Procedure 30.1. Verifying the Initial RAM Disk Image

1. As root, list the contents in the /boot/ directory and find the kernel (vmlinuz-<kernel_version>) and initramfs-<kernel_version> with the latest (most recent) version number:

   Example 30.1. Ensuring that the kernel and initramfs versions match

   ~]# ls /boot/
   config-2.6.32-17.el6.x86_64           lost+found
   config-2.6.32-19.el6.x86_64           symvers-2.6.32-17.el6.x86_64.gz
   config-2.6.32-22.el6.x86_64           symvers-2.6.32-19.el6.x86_64.gz
   efi                                   symvers-2.6.32-22.el6.x86_64.gz
   grub                                  System.map-2.6.32-17.el6.x86_64
   initramfs-2.6.32-17.el6.x86_64.img    System.map-2.6.32-19.el6.x86_64
   initramfs-2.6.32-19.el6.x86_64.img    System.map-2.6.32-22.el6.x86_64
   initramfs-2.6.32-22.el6.x86_64.img    vmlinuz-2.6.32-17.el6.x86_64
   initrd-2.6.32-17.el6.x86_64kdump.img  vmlinuz-2.6.32-19.el6.x86_64
   initrd-2.6.32-19.el6.x86_64kdump.img  vmlinuz-2.6.32-22.el6.x86_64
   initrd-2.6.32-22.el6.x86_64kdump.img

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   Example 30.1, “Ensuring that the kernel and initramfs versions match” shows that:
   • we have three kernels installed (or, more correctly, three kernel files are present in /boot/),
   • the latest kernel is vmlinuz-2.6.32-22.el6.x86_64, and
   • an initramfs file matching our kernel version, initramfs-2.6.32-22.el6.x86_64.img, also exists.

   Important

   In the /boot/ directory you may find several initrd-<version>kdump.img 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.
2. (Optional) If your initramfs-<kernel_version> 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:

   ~]# dracut

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   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 initramfs file:

   ~]# dracut
   Will not override existing initramfs (/boot/initramfs-2.6.32-22.el6.x86_64.img) without --force

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   You can create an initramfs in the current directory by calling dracut <initramfs_name> <kernel_version>:

   ~]# dracut "initramfs-$(uname -r).img" $(uname -r)

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   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="<module> [<more_modules>]" 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 lsinitrd <initramfs_file> command:

   ~]# lsinitrd initramfs-2.6.32-22.el6.x86_64.img
   initramfs-2.6.32-22.el6.x86_64.img:
   ========================================================================
   dracut-004-17.el6
   ========================================================================
   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
   [output truncated]

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   See man dracut and man dracut.conf for more information on options and usage.
3. Examine the grub.conf configuration file in the /boot/grub/ directory to ensure that an initrd initramfs-<kernel_version>.img exists for the kernel version you are booting. See Section 30.6, “Verifying the Boot Loader” for more information.