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Description of problem:

The mkinitrd script is not taking into account command_names
from LVM's configuration. This parameter can modify the output of 
an LVM command, and therefore the parsing can go wrong, generating initramfs with no LVM and no device-mapper, and causing issues at boot time.

Version-Release number of selected component (if applicable):
dracut-033-502.el7.x86_64, but I've checked the code in 7.5 and the problem is still there.

How reproducible:
Always.

Steps to Reproduce:
1. Modify /etc/lvm/lvm.conf and change 'command_names = 0' to 'command_names = 1'. You don't need to edit 'prefix" at all.
2. Re-create the initramfs with 'dracut -f'
3. Boot the server.

Actual results:
The server will go into emergency mode.

Expected results:
The server should boot without problems.

Additional info:
This is very similar to the issue reported in bz#593096 . The patch attached here is based in that one, but in our case I had to modify dracut-functions.sh.

Created attachment 1377439 [details]
proposed patch

Created attachment 1389542 [details]
second version based on upstream code

Lukáš, I've posted a new version of the patch based on upstream code I backported. 
After running more tests in Fedora with the code from 'dracutdevs' git, I found that it actually didn't show the issue at all. After backporting the changes you can see in the patch, the problem was fixed in RHEL 7. 
Does this new patch look good to you?
I'll build a rpm soon so it can be tested by QA.

Yep, looks good to me. The only problem is that we are passed beta right now, so only blockers and exceptions are accepted to rhel-7.5.

https://github.com/dracutdevs/dracut/commit/15384bcedb8002440e1327e97cd9c139af8a32dd -> post

Looks fixed in dracut-033-547.el7.x86_64. (RHEL-7.6-20180720.9)

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:3232