[CentOS] Issues booting centos7 [dracut is failing to enable centos/root, centos/swap LVs]

Yannis Milios yannis.milios at gmail.com
Mon Jul 30 15:26:43 UTC 2018


Hello,

I'm having a strange problem booting a new centos7 installation. Below some
background on this. [I have attached the tech details at the bottom of this
message]

I started a new CentOS7 installation on a VM, so far all good, o/s boots
fine. Then I decided to increase VM disk size (initially was 10G) to 13G.
Powered off the VM, increased the vhd via the hypervisor, booted from
CentOS livecd, selected "recover my centos installation". Then I used the
following sequence of commands to make the new vhd size "visible" to the
o/s ...

- ran fdisk /dev/sda and deleted partition 2. (This is the LVM partition
where the o/s is stored. The first partition is /boot [xfs] partition *non
lvm*.)
- created a new partition with same starting sector as before deleting it,
but a different ending sector (to reflect to the increased space).
- set partition type to 8e (lvm), saved settings and exit.
- ran pvresize and lvresize to make new space visible to the o/s.All good,
I can see the space increase on 'lvdisplay centos/root'.
- ran 'mount /dev/mapper/centos-root /mnt/root' to temporarily mount the
o/s partition.
- ran 'xfs_growfs /mnt/root' to resize the o/s fs to the new size. It was
successful and I could actually chroot to the o/s and verify new disk size.
- rebooted  and tried to boot from hdd this time. Grub menu shows up and
loads default kernel (3.10.0-862.9.1.el7.x86_64).
- after initial kernel boot up process, booting continues to initrd and
then it's where the problem starts...
- looks like dracut has issues locating/enabling /dev/mapper/centos-root
(lv) and as a result it cannot boot to the 'real' root fs (/).
- while in dracut shell, I execute the following command sequence:
      1. lvm lvchange -ay /dev/centos/root
      2. lvm lvchange -ay /dev/centos/swap
      3. ln -s /dev/mapper/centos-root /dev/root
      4. exit
...and the o/s boots fine...so looks like the pv,vg,lv is detected properly
while in initrd, but somehow dracut has difficulties enabling the root,swap
LVs ?

- While in o/s, I rebuild initrd by using: 'dracut -f -v -a lvm'
Note, I have to use '-a lvm' as for some reason, if don't, the lvm utils
(lvm,lvm_scan) are not being included to the initrd, not sure why this
happens.
After rebooting, same thing happens, I have to manually boot the system via
dracut shell.

I'm a bit stuck at this point, any clues what I'm doing wrong in here ?

As I previously said, this is a new installation, so I could simply
reinstall the whole thing, but I would rather try to find out some answer
to why is this happening ... :-) [curiosity]

Some additional details:
==================
I've attached /run/initramfs/rdsosreport.txt file [generated while in
inird] here:
https://privatebin.net/?fdc4052c0c402884#gdB/QYR3IeR55SxUbjfrkZPQfJ7jMxiUxq5DWhTVbWc=

o/s ver=CentOS Linux release 7.5.1804 (Core)

[root at localhost ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   13G  0 disk
├─sda1            8:1    0  500M  0 part /boot
└─sda2            8:2    0 12.5G  0 part
  ├─centos-root 253:0    0 11.5G  0 lvm  /
  └─centos-swap 253:1    0    1G  0 lvm  [SWAP]

[root at localhost ~]# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="rd.lvm.lv=centos/root rd.lvm.lv=centos/swap rd.shell
rhgb"
GRUB_DISABLE_RECOVERY="true"



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