[CentOS] Xen, Amazon, and /proc/cmdline

[Kwan Lowe]

On Tue, Jan 26, 2010 at 2:48 PM, Kurt Newman
<knewman at globaldataguard.com> wrote:
> Amazon (or perhaps Amazon's configuration of Xen) forces a machine to
> come up at run level 4, regardless of what's in /etc/inittab.
>
> I've looked through /etc/rc.sysinit and /etc/rc.d/rc, to determine which
> (if any script) looks at /proc/cmdline and forces a particular run
> level, but to no avail.
>

> It seems that /sbin/init does the forcing.  Can anyone confirm that
> /sbin/init reads /proc/cmdline to overwrite /etc/inittab?  I can't seem
> to find any reference in man pages or searching the web.

You *can* override the initdefault in inittab via the kernel option,
but if you're not seeing it in /proc/cmdline it's likely some other rc
script.  I saw some references to this being controlled via xen:

http://somic.org/2008/06/20/ec2-instances-always-boot-to-runlevel-4/

Alas, the links are dead...  Another site shows:

http://www.novell.com/support/search.do?cmd=displayKC&docType=kc&externalId=7001985&sliceId=1&docTypeID=DT_TID_1_1

---quote
Xen para-virtual SLE (all versions), first method
This method uses the legacy installation file. Any hardware changes
made to a managed domain via "YaST", "virt-manager" or "xm commands"
will not be present.  Replace "DOMU" with the name of your DomU.

   1. Go to /etc/xen/vm
   2. Locate the installation file, usually the name of the Xen DomU
   3. Use the "xm create" command. (The -c will connect to the
console, and xencons=xvc0 will use the Xen frame buffer for SLES 10
SP1 and higher, and SLES 9 SP4. Use xencons=tty for SLES 10).
      xm create -c DOMU extra=" init 1 xencons=xvc0"
   4. Shutdown the DomU after making changes
   5. Start the DomU normally"
---quote

So it may be being passed through xen which might not show up in
proc/cmdline (can't test right now).