[CentOS] How to PXE kickstart hosts with little memory (Error: "Warning: /dev/root does not exist")?

Hi,

while kickstarting our virtual machines with PXE we often run into 
kickstart/anaconda failing with


[...]
[...] dracut-mount[xxx]: Warning: Can't mount root filesystem
[...] dracut-mount[xxx]: Warning: /dev/root does not exist
[...] dracut-mount[xxx]:/lib/dracut-lib.sh: line 1030: echo write error: 
No space left on device
         Starting Dracut Emergency Shell...
Warning: /dev/root does not exist

Generating "/run/initramfs/rsdosreport.txt"

[...]


It seems, that this is not related to local disk space - as I initally 
thought - but to too small memory.  It only happens with VMs with little 
RAM (1024 MB).  As soon as we raise the available memory to 2048 MB, 
kickstarting works fine.  The RHEL 7 installation guide states, that the 
minimal memory requirement is 1 GB, so the network installation /should/ 
work.

Is there a way to install such hosts w/o having to temporarily raise the 
available memory?

Cheers
frank