bootloader --append does exactly what you'd think it does:  it appends the text you provide to the default bootloader argument list.  For most machines and most install configurations, the default list is "rhgb quiet".  This has been how it's worked for as long as I can remember.

If you need to modify this default list, you'll need to do some mangling in a %post script.  I'm not going to overload the meaning of --append to also sometimes mean "set".

(In reply to comment #1)
> bootloader --append does exactly what you'd think it does:  it appends the text
> you provide to the default bootloader argument list.  For most machines and
> most install configurations, the default list is "rhgb quiet".  This has been
> how it's worked for as long as I can remember.
> 
> If you need to modify this default list, you'll need to do some mangling in a
> %post script.  I'm not going to overload the meaning of --append to also
> sometimes mean "set".    

I think you misunderstood:
The default anaconda-ks.cfg file created when one installs RHEL 6 contains the line:
bootloader --location=mbr --driveorder=sda --append="rhgb quiet"

if one changes that line to:
bootloader --location=mbr --append=""
or:
bootloader --location=mbr

And then does a new install with the modified anaconda-ks.cfg file passed to it:
"rhgb quiet" is _still_ appended to the kernel line in grub.conf

This is not the expected behavior nor is it the default behavior of RHEL in the past (neither RHEL 5 or RHEL 4 will do this).

The kernel line generated for grub in when "bootloader --location=mbr" is passed in RHEL 5 is:
	kernel /vmlinuz-2.6.18-194.el5 ro root=LABEL=/

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.

> I think you misunderstood:

Nope.

> if one changes that line to:
> bootloader --location=mbr --append=""
> or:
> bootloader --location=mbr
> 
> And then does a new install with the modified anaconda-ks.cfg file passed to
> it:
> "rhgb quiet" is _still_ appended to the kernel line in grub.conf

Right.  "rhgb quiet" are the anaconda defaults.  You always get these.  It's part of setting up the post-installation environment.  bootloader --append only appends arguments to the default list.  It does not set the bootloader argument list.  That's why it's called --append.  Therefore using bootloader --append="" will still get you the string "rhgb quiet".  Similarly if you remove it entirely.

> This is not the expected behavior nor is it the default behavior of RHEL in the
> past (neither RHEL 5 or RHEL 4 will do this).

It is the expected behavior, as documented here:

http://fedoraproject.org/wiki/Anaconda/Kickstart#bootloader

Another thing to note is that since anaconda determines if it should add "rhgb quiet" to the default arguments based on whether or not have packages installed that provide 'rhgb' or 'plymouth', you could remove those packages from your transaction set.

Adding the following to your %packages section would prevent 'rhgb quiet' being added to your boot argument list (rhgb has been deprecated in favor of plymouth in RHEL-6):

    -plymouth

In the case where you do want plymouth installed, but don't want to use it for the boot up screen, you'll have to modify the boot loader configuration file in a %post script or by hand.

Thanks for the hint on plymouth, unfortunately that doesn't work.

What I mean is, even though -plymouth is there in the kickstart file, it doesn't remove the package.

So i tried removing anything with plymouth in the name, and all the dependencies of said packages:
-kexec-tools
-dracut-kernel
-dracut
-plymouth-core-libs
-plymouth-scripts
-plymouth

The only one out of that entire list that was actually removed was:
kexec-tools

dracut-kernel, dracut, plymouth-core-libs, plymouth-scripts, & plymouth were all still installed, even though they were in the kickstart file to be removed.

They are all also listed in the anaconda-ks.cfg file that is saved in root after the install finished.

My entire packages section consisted of:
%packages
@base
@core
-Red_Hat_Enterprise_Linux-Release_Notes-6-en-US
-kexec-tools
-dracut-kernel
-dracut
-plymouth-core-libs
-plymouth-scripts
-plymouth

Is there some unknown dependency I'm missing here?

--thanks

plymouth probably still gets pulled in due to kernel dependencies, though.  I bet it's needed for the kernel's install scriptlet  Really if you need to mangle the bootloader args, you're going to have to do something in a %post script.