Commit e5731b58 authored by Boqun Feng's avatar Boqun Feng Committed by Paul E. McKenney

rcutorture/doc: Create initrd using dracut

Using dracut is another way to get an initramfs for KVM-based RCU
torture tests, which is more flexible than using the host's initramfs
image, because modules and binaries may be added or removed via dracut
command options. So add an example in the document, in case that there
are some situations where host's initramfs couldn't be used.
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 750db0f5
......@@ -13,6 +13,22 @@ cd initrd
cpio -id < /tmp/initrd.img.zcat
------------------------------------------------------------------------
Another way to create an initramfs image is using "dracut"[1], which is
available on many distros, however the initramfs dracut generates is a cpio
archive with another cpio archive in it, so an extra step is needed to create
the initrd directory hierarchy.
Here are the commands to create a initrd directory for rcutorture using
dracut:
------------------------------------------------------------------------
dracut --no-hostonly --no-hostonly-cmdline --module "base bash shutdown" /tmp/initramfs.img
cd tools/testing/selftests/rcutorture
mkdir initrd
cd initrd
/usr/lib/dracut/skipcpio /tmp/initramfs.img | zcat | cpio -id < /tmp/initramfs.img
------------------------------------------------------------------------
Interestingly enough, if you are running rcutorture, you don't really
need userspace in many cases. Running without userspace has the
advantage of allowing you to test your kernel independently of the
......@@ -89,3 +105,9 @@ while :
do
sleep 10
done
------------------------------------------------------------------------
References:
[1]: https://dracut.wiki.kernel.org/index.php/Main_Page
[2]: http://blog.elastocloud.org/2015/06/rapid-linux-kernel-devtest-with-qemu.html
[3]: https://www.centos.org/forums/viewtopic.php?t=51621
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