升级linux内核时，2.6.21.5内核编译成功，但启动时出现panic，请看问题详细描述！
原有系统：Red   Hat   Enterprise   Linux   AS   (2.6.9-34.EL)
升级到内核版本：2.6.21.5

内核编译时成功，并且make   install   后也自动更新了/root/grub/grub.conf文件，该文件内容如下：
#boot=/dev/hda
default=1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title   Red   Hat   Enterprise   Linux   AS   (2.6.21.5)
            root   (hd0,0)
            kernel   /vmlinuz-2.6.21.5   ro   root=/dev/VolGroup00/LogVol00   rhgb   quiet
            initrd   /initrd-2.6.21.5.img
title   Red   Hat   Enterprise   Linux   AS   (2.6.9-34.EL)
            root   (hd0,0)
      kernel   /vmlinuz-2.6.9-34.EL   ro   root=/dev/VolGroup00/LogVol00   rhgb   quiet
            initrd   /initrd-2.6.9-34.EL.img

但是我以2.6.21.5内核启动时，出现错误，错误信息如下：
/proc/misc:   No   entry   for   devicemapper   found
Is   device-mapper   driver   missing   from   kernel?
Failure   to   communicate   with   kernel   device-mapper   driver.
0   logical   volume(s)   in   volume   group   "VolGroup00 "   now   active
mount:   error   19   mounting   ext3
mount:   error   2   mounting   none
switchroot:   mount   failed:   22
umount   /initrd/dev   failed:   2
kernel   panic   -   not   symcing:   Attempted   to   kill   init!


------解决方案--------------------
Is device-mapper driver missing from kernel?
------解决方案--------------------
因为你的磁盘做了LVM，编译内核时记得选中 LVM support