I recently added a 2nd HDD to a system and then proceeded to do a clean install on to this 2nd HDD of CentOS 6.5. The original system was CentOS 5.9. My plan was to leave the original HDD in place so that I could pull data off of it as needed as we migrated several KVMs from HDD #1 to HDD #2.All this went uneventfully, and I didn't even bother to remove HDD #1, figuring we'd get around to it.So fast forward to today and I actually attempted to remove HDD #1 and lo and behold I can't. Booting CentOS 6.5 off of HDD #2 seems to know about the original HDD and kernel panics when HDD #1 is removed.        The setup of this box is vanilla CentOS 6.5 with the Virtualization* YUM groups installed. There is no reference to HDD #1 in HDD #2's /etc/fstab. The only area where I would consider digging deeper is with LVM, since CentOS installs (all Red Hat distros for that matter) make use of LVM when setting up their HDDs.Here's the stanza from /etc/grub.conf in case that might be helpful:title CentOS (2.6.32-431.17.1.el6.x86_64)    root (hd0,0)    kernel /vmlinuz-2.6.32-431.17.1.el6.x86_64 ro root=/dev/mapper/vg_catbus-lv_root rd_NO_LUKS rd_LVM_LV=vg_catbus/lv_root LANG=en_US.UTF-8 rd_LVM_LV=vg_catbus/lv_swap rd_NO_MD quiet SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto rd_LVM_LV=VolGroup00/LogVol01  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM    initrd /initramfs-2.6.32-431.17.1.el6.x86_64.imgHere too is the LVM setup:$ sudo vgs  VG         #PV #LV #SN Attr   VSize   VFree  VolGroup00   1   3   0 wz--n- 465.66g    0   vg_catbus    1   3   0 wz--n-   1.82t    0 $ sudo lvs  LV       VG         Attr       LSize   Pool Origin Data%  Move Log Cpy%Sync Convert  LogVol00 VolGroup00 -wi-a----- 442.19g                                               LogVol01 VolGroup00 -wi-ao----  13.69g                                               LogVol02 VolGroup00 -wi-a-----   9.78g                                               lv_home  vg_catbus  -wi-ao----   1.76t                                               lv_root  vg_catbus  -wi-ao----  50.00g                                               lv_swap  vg_catbus  -wi-ao----  13.77g           $ sudo pvs  PV         VG         Fmt  Attr PSize   PFree  /dev/sda2  vg_catbus  lvm2 a--    1.82t    0   /dev/sdb2  VolGroup00 lvm2 a--  465.66g    0 Key pointsSystem crashes when I shutdown down the system, physically disconnect HDD #1, and then power the system back up.The 500GB HDD is what I'm calling HDD #1, the 2TB HDD is what I'm calling HDD #2.With HDD #1 connected, I can boot the system just fine.
Removal of HDD causes kernel panic
linux;centos;lvm;kernel panic;grub legacy
The key item to notice in the output of /etc/grub.conf are these types of arguments being passed to the kernel:rd_LVM_LV=VolGroup00/LogVol01Removing this argument from GRUB's linux .. line resolved the issue. These are remnants of HDD #1's LVM. These were added automatically by the install to assist you, but in this case, it's caused this pseudo dependency on HDD #1 even when there isn't actually a real one.Simply removing this line from /etc/grub.conf resolves it. title CentOS (2.6.32-431.17.1.el6.x86_64)    root (hd0,0)    kernel /vmlinuz-2.6.32-431.17.1.el6.x86_64 ro root=/dev/mapper/vg_catbus-lv_root rd_NO_LUKS rd_LVM_LV=vg_catbus/lv_root LANG=en_US.UTF-8 rd_LVM_LV=vg_catbus/lv_swap rd_NO_MD quiet SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM    initrd /initramfs-2.6.32-431.17.1.el6.x86_64.imgTake care when making these edits and also be sure to remove them from any of the other title entries you may have in your /etc/grub.conf too.