How to have dracut conditionally add different kernel modules for different kernels?

How to have dracut conditionally add different kernel modules for different kernels?

[lyndat3-p/IIKWkZnU0S+FvcfC7Uqw]

The distro I use, opensuse, has switched to using dracut for initrd creation.

Prior to dracut usage, kernel-flavor-specific loading -- particularly for the case of Xen -- could be defined in

 /etc/sysconfig/kernel
  ...
  INITRD_MODULES="processor thermal ahci fan jbd ext3 edd"
  DOMU_INITRD_MODULES="xennet xenblk"
  ...

On 'old' mkinitrd, if both -xen and non-xen kernels were installed, initrd's were created for each.  In the xen case the modules defined in "DOMU_INITRD_MODULES" were conditionally added to the initrd-xen.

Since the  switch to dracut, module config/loading is defined in dracut.conf & dracut.d/*conf

But the 

add_drivers+=" ... " 

is apparently added for all kernels.

What's the right way to add kernel-specific modules in dracut, so that for example the xen mods are ONLY added in the xen case?

LT

Re: How to have dracut conditionally add different kernel modules for different kernels?

[Andrei Borzenkov]

В Fri, 10 Apr 2015 12:11:53 -0700
lyndat3-p/IIKWkZnU0S+FvcfC7Uqw@public.gmane.org пишет:

> The distro I use, opensuse, has switched to using dracut for initrd creation.
> 
> Prior to dracut usage, kernel-flavor-specific loading -- particularly for the case of Xen -- could be defined in
> 
>  /etc/sysconfig/kernel
>   ...
>   INITRD_MODULES="processor thermal ahci fan jbd ext3 edd"
>   DOMU_INITRD_MODULES="xennet xenblk"
>   ...
> 
> On 'old' mkinitrd, if both -xen and non-xen kernels were installed, initrd's were created for each.  In the xen case the modules defined in "DOMU_INITRD_MODULES" were conditionally added to the initrd-xen.
> 
> Since the  switch to dracut, module config/loading is defined in dracut.conf & dracut.d/*conf
> 
> But the 
> 
> add_drivers+=" ... " 
> 
> is apparently added for all kernels.
> 
> What's the right way to add kernel-specific modules in dracut, so that for example the xen mods are ONLY added in the xen case?

Not sure about the "right" way, but dracut configuration files are
shell scripts, so you can implement the same logic in /etc/dracut.d
snippet, something like

if is_xen_kernel ; then
  add_drivers+=" ..."
fi

where is_xen_kernel does whatever check is required to detect domU
kernel.

Re: How to have dracut conditionally add different kernel modules for different kernels?

[lyndat3-p/IIKWkZnU0S+FvcfC7Uqw]

On Sun, Apr 12, 2015, at 01:11 AM, Andrei Borzenkov wrote:
> > What's the right way to add kernel-specific modules in dracut, so that for example the xen mods are ONLY added in the xen case?
> 
> Not sure about the "right" way, but dracut configuration files are
> shell scripts, so you can implement the same logic in /etc/dracut.d
> snippet, something like
> 
> if is_xen_kernel ; then
>   add_drivers+=" ..."
> fi
> 
> where is_xen_kernel does whatever check is required to detect domU
> kernel.

Option to use if ...  should do the trick.

Detecting if xen is RUNNING is

if test -d /proc/xen; then
 whatver
fi

But that's not the needed test.  Like you said have to get a test that checks if the dracut TARGET is a xen kernel.  When dracut's running across multiple xen & non-xen kernels, I'm not yet sure how to hook that info from inside dracut.conf.

LT