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-rw-r--r--tools/testing/selftests/rcutorture/doc/rcu-test-image.txt41
1 files changed, 33 insertions, 8 deletions
diff --git a/tools/testing/selftests/rcutorture/doc/rcu-test-image.txt b/tools/testing/selftests/rcutorture/doc/rcu-test-image.txt
index 449cf579d6f9..b2fc247976b1 100644
--- a/tools/testing/selftests/rcutorture/doc/rcu-test-image.txt
+++ b/tools/testing/selftests/rcutorture/doc/rcu-test-image.txt
@@ -1,8 +1,33 @@
-This document describes one way to create the rcu-test-image file
-that contains the filesystem used by the guest-OS kernel. There are
-probably much better ways of doing this, and this filesystem could no
-doubt be smaller. It is probably also possible to simply download
-an appropriate image from any number of places.
+Normally, a minimal initrd is created automatically by the rcutorture
+scripting. But minimal really does mean "minimal", namely just a single
+root directory with a single statically linked executable named "init":
+
+$ size tools/testing/selftests/rcutorture/initrd/init
+ text data bss dec hex filename
+ 328 0 8 336 150 tools/testing/selftests/rcutorture/initrd/init
+
+Suppose you need to run some scripts, perhaps to monitor or control
+some aspect of the rcutorture testing. This will require a more fully
+filled-out userspace, perhaps containing libraries, executables for
+the shell and other utilities, and soforth. In that case, place your
+desired filesystem here:
+
+ tools/testing/selftests/rcutorture/initrd
+
+For example, your tools/testing/selftests/rcutorture/initrd/init might
+be a script that does any needed mount operations and starts whatever
+scripts need starting to properly monitor or control your testing.
+The next rcutorture build will then incorporate this filesystem into
+the kernel image that is passed to qemu.
+
+Or maybe you need a real root filesystem for some reason, in which case
+please read on!
+
+The remainder of this document describes one way to create the
+rcu-test-image file that contains the filesystem used by the guest-OS
+kernel. There are probably much better ways of doing this, and this
+filesystem could no doubt be smaller. It is probably also possible to
+simply download an appropriate image from any number of places.
That said, here are the commands:
@@ -36,7 +61,7 @@ References:
https://help.ubuntu.com/community/JeOSVMBuilder
http://wiki.libvirt.org/page/UbuntuKVMWalkthrough
http://www.moe.co.uk/2011/01/07/pci_add_option_rom-failed-to-find-romfile-pxe-rtl8139-bin/ -- "apt-get install kvm-pxe"
- http://www.landley.net/writing/rootfs-howto.html
- http://en.wikipedia.org/wiki/Initrd
- http://en.wikipedia.org/wiki/Cpio
+ https://www.landley.net/writing/rootfs-howto.html
+ https://en.wikipedia.org/wiki/Initrd
+ https://en.wikipedia.org/wiki/Cpio
http://wiki.libvirt.org/page/UbuntuKVMWalkthrough