Description of problem:
RHEL 7.6 dracut-iniqueue script has a default value of 180 seconds (as defined in the RDRETRY variable), which is higher than systemd root mount service (90 seconds). This can lead to unbootable system when root resides on a degraded software RAID1 device (user is dropped to emergency shell). See https://bugzilla.redhat.com/show_bug.cgi?id=1451660# for an example of the problem. Note that this only happen when the RAID device expects itself to be healthy, but it unexpectedly found the array degraded during boot.

Passing "rd.retry=30" at boot time fixes the degraded array boot problem, as the array is forced started before the systemctl root mount service times out. Moreover, the long dracut rd.retry timeout is inconsistent with dracut.cmdline(7) man page, where it is stated the timeout should be 30 seconds.

Version-Release number of selected component (if applicable):
dracut-033-554.el7.x86_64

How reproducible:
Install OS on a MD RAID1 array, shutdown the system, remove a drive and poweron the system. User is dropped to an emergency shell.

Steps to Reproduce:
1. Install OS on a MD RAID1 array
2. Shutdown the system
3. Remove a drive (with system powered off)
4. Power on the system
5. After ~90s, user is droppen in a emergency shell

Actual results:
OS does not boot properly when a RAID1 array is unexpectedly found degraded.

Expected results:
RAID1 should have no problem booting from a degraded array.

Additional info:
I traced the problem to how mdadm --incremental, dracut timeout (rd.retry) and systemctl default timeout interact:
- mdadm --incremental will not start/run an array which is unexpectedly found degraded;
- dracut should force-start the array after 2/3 of the timeout value passed. With current RHEL default, this amount to 180/3*2 = 120s;
- systemctl expect to mount the root filesystem in at most 90s. If it does not succeed, it abort the dracut script and drop to an emergency shell. Being 90s lower than dracut timeout, it means that dracut does not have a chance to force-start the array.
Lowering rd.retry timeout (setting as the man page suggests) enables dracut to force-start the array, allowing the systemctl service to succeed.