CentOS - Apr 2017 - 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

On 04/21/2017 12:49 PM, Frank Thommen wrote:
>
> 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.
Yeah, I filed a bug report against the documentation some time ago.

https://bugzilla.redhat.com/show_bug.cgi?id=1410948

...though bugzilla is currently down.
> Is there a way to install such hosts w/o having to temporarily raise 
> the available memory? 

None that I'm aware of, as of 7.3.  If you have a 7.2 install tree, you 
can boot the older installer and then update the installed system.  
Seems easier to boost the memory, typically.

On 04/21/2017 10:25 PM, Gordon Messmer wrote:
> On 04/21/2017 12:49 PM, Frank Thommen wrote:
>>
>> 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.
>
> Yeah, I filed a bug report against the documentation some time ago.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1410948
>
> ...though bugzilla is currently down.
>
>> Is there a way to install such hosts w/o having to temporarily raise
>> the available memory?
>
>
> None that I'm aware of, as of 7.3.  If you have a 7.2 install tree, you
> can boot the older installer and then update the installed system.
> Seems easier to boost the memory, typically.
I gave it a try with 7.2.1511 and that works fine as long as I have 
"ip=eth0:dhcp" in my PXE config.  As soon as I expand it to 
"ip=eth0:dhcp ip=eno1:dhcp rd.neednet=1" (I do that to make sure 
kickstart works independently from the name of the network interface), 
kickstart enters into emergency mode w/o any error message after a lot 
of timeout warnings.  However that's something we can work around.

Thanks for the 7.2 hint.

frank