Add 'set-kernel'/'get-kernel'/LIBGUESTFS_KERNEL to override appliance kernel.

This allows you to override the appliance kernel with an easy
command or environment variable.

4 files changed, 57 insertions, 1 deletions

diff --git a/guestfish.pod b/guestfish.pod
index f2255f16..6f35ac46 100644
--- a/guestfish.pod
+++ b/guestfish.pod
@@ -553,6 +553,10 @@ Pass additional options to the guest kernel.
 Set C<LIBGUESTFS_DEBUG=1> to enable verbose messages.  This has the
 same effect as using the B<-v> option.
 
+=item LIBGUESTFS_KERNEL
+
+Override the ordinary selection of appliance kernel.
+
 =item LIBGUESTFS_MEMSIZE
 
 Set the memory allocated to the qemu process, in megabytes.  For
diff --git a/guestfs.pod b/guestfs.pod
index 4235454e..9e0d4d31 100644
--- a/guestfs.pod
+++ b/guestfs.pod
@@ -917,6 +917,10 @@ Pass additional options to the guest kernel.
 Set C<LIBGUESTFS_DEBUG=1> to enable verbose messages.  This
 has the same effect as calling C<guestfs_set_verbose (handle, 1)>.
 
+=item LIBGUESTFS_KERNEL
+
+Override the ordinary selection of appliance kernel.
+
 =item LIBGUESTFS_MEMSIZE
 
 Set the memory allocated to the qemu process, in megabytes.  For
diff --git a/src/generator.ml b/src/generator.ml
index 8751bb5a..398fd04b 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -530,6 +530,31 @@ guest kernel command line.
 
 If C<NULL> then no options are added.");
 
+  ("set_kernel", (RErr, [String "kernel"]), -1, [FishAlias "kernel"],
+   [],
+   "override the normal appliance kernel",
+   "\
+This function lets you override the ordinary selection
+of kernel used in the appliance.
+
+The default is C<NULL> unless overridden by setting
+C<LIBGUESTFS_KERNEL> environment variable.
+
+Setting C<kernel> to C<NULL> means the ordinary appliance
+kernel is selected by the usual means.");
+
+  ("get_kernel", (RConstString "kernel", []), -1, [],
+   (* This cannot be tested with the current framework.  The
+    * function can return NULL in normal operations, which the
+    * test framework interprets as an error.
+    *)
+   [],
+   "get the override appliance kernel",
+   "\
+Return the override appliance kernel (see C<guestfs_set_kernel>).
+
+If C<NULL> then the ordinary appliance kernel is used.");
+
   ("set_autosync", (RErr, [Bool "autosync"]), -1, [FishAlias "autosync"],
    [],
    "set autosync mode",
diff --git a/src/guestfs.c b/src/guestfs.c
index db6db910..5750a4f4 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -174,6 +174,7 @@ struct guestfs_h
   char *path;			/* Path to kernel, initrd. */
   char *qemu;			/* Qemu binary. */
   char *append;			/* Append to kernel command line. */
+  char *kernel;			/* Override appliance kernel. */
 
   int memsize;			/* Size of RAM (megabytes). */
 
@@ -249,6 +250,12 @@ guestfs_create (void)
     if (!g->append) goto error;
   }
 
+  str = getenv ("LIBGUESTFS_KERNEL");
+  if (str) {
+    g->kernel = strdup (str);
+    if (!g->kernel) goto error;
+  }
+
   /* Choose a suitable memory size.  Previously we tried to choose
    * a minimal memory size, but this isn't really necessary since
    * recent QEMU and KVM don't do anything nasty like locking
@@ -674,6 +681,22 @@ guestfs_get_append (guestfs_h *g)
 }
 
 int
+guestfs_set_kernel (guestfs_h *g, const char *kernel)
+{
+  free (g->kernel);
+  g->kernel = NULL;
+
+  g->kernel = kernel ? safe_strdup (g, kernel) : NULL;
+  return 0;
+}
+
+const char *
+guestfs_get_kernel (guestfs_h *g)
+{
+  return g->kernel;
+}
+
+int
 guestfs_set_memsize (guestfs_h *g, int memsize)
 {
   g->memsize = memsize;
@@ -1058,7 +1081,7 @@ guestfs_launch (guestfs_h *g)
     add_cmdline (g, memsize_str);
     add_cmdline (g, "-no-reboot"); /* Force exit instead of reboot on panic */
     add_cmdline (g, "-kernel");
-    add_cmdline (g, (char *) kernel);
+    add_cmdline (g, g->kernel ? : (char *) kernel);
     add_cmdline (g, "-initrd");
     add_cmdline (g, (char *) initrd);
     add_cmdline (g, "-append");