Add --squashfs-only option to drop inner rootfs.img layer

Make runtime directly into squashfs image. This reduces largely
unreproducible ext4 layer, but requires anaconda's dracut module
modification to properly mount the image.

src/pylorax/__init__.py

@@ -186,7 +186,8 @@ class Lorax(BaseLoraxClass):
             add_arch_templates=None,
             add_arch_template_vars=None,
             verify=True,
-            user_dracut_args=None):
+            user_dracut_args=None,
+            squashfs_only=False):
 
         assert self._configured
 
@@ -332,9 +333,16 @@ class Lorax(BaseLoraxClass):
                 compressargs += ["-Xbcj", self.arch.bcj]
             else:
                 logger.info("no BCJ filter for arch %s", self.arch.basearch)
-        rb.create_runtime(joinpaths(installroot,runtime),
-                          compression=compression, compressargs=compressargs,
-                          size=size)
+        if squashfs_only:
+            # Create an ext4 rootfs.img and compress it with squashfs
+            rb.create_squashfs_runtime(joinpaths(installroot,runtime),
+                compression=compression, compressargs=compressargs,
+                size=size)
+        else:
+            # Create an ext4 rootfs.img and compress it with squashfs
+            rb.create_ext4_runtime(joinpaths(installroot,runtime),
+                compression=compression, compressargs=compressargs,
+                size=size)
         rb.finished()
 
         logger.info("preparing to build output tree and boot images")

src/pylorax/cmdline.py

@@ -109,6 +109,8 @@ def lorax_parser(dracut_default=""):
                           help="Do not verify SSL certificates")
     optional.add_argument("--dnfplugin", action="append", default=[], dest="dnfplugins",
                           help="Enable a DNF plugin by name/glob, or * to enable all of them.")
+    optional.add_argument("--squashfs-only", action="store_true", default=False,
+                          help="Use a plain squashfs filesystem for the runtime.")
 
     # dracut arguments
     dracut_group = parser.add_argument_group("dracut arguments")

src/pylorax/creator.py

@@ -203,7 +203,7 @@ def make_runtime(opts, mount_dir, work_dir, size=None):
     rb = RuntimeBuilder(product, arch, fake_dbo)
     compression, compressargs = squashfs_args(opts)
     log.info("Creating runtime")
-    rb.create_runtime(joinpaths(work_dir, RUNTIME), size=size,
+    rb.create_ext4_runtime(joinpaths(work_dir, RUNTIME), size=size,
                       compression=compression, compressargs=compressargs)
 
 

src/pylorax/treebuilder.py

@@ -215,7 +215,16 @@ class RuntimeBuilder(object):
             runcmd(["depmod", "-a", "-F", ksyms, "-b", root, kernel.version])
             generate_module_info(moddir+kernel.version, outfile=moddir+"module-info")
 
-    def create_runtime(self, outfile="/var/tmp/squashfs.img", compression="xz", compressargs=None, size=2):
+    def create_squashfs_runtime(self, outfile="/var/tmp/squashfs.img", compression="xz", compressargs=None, size=2):
+        """Create a plain squashfs runtime"""
+        compressargs = compressargs or []
+        os.makedirs(os.path.dirname(outfile))
+
+        # squash the rootfs
+        imgutils.mksquashfs(self.vars.root, outfile, compression, compressargs)
+
+    def create_ext4_runtime(self, outfile="/var/tmp/squashfs.img", compression="xz", compressargs=None, size=2):
+        """Create a squashfs compressed ext4 runtime"""
         # make live rootfs image - must be named "LiveOS/rootfs.img" for dracut
         compressargs = compressargs or []
         workdir = joinpaths(os.path.dirname(outfile), "runtime-workdir")

src/sbin/lorax

@@ -145,7 +145,8 @@ def main():
               add_arch_templates=opts.add_arch_templates,
               add_arch_template_vars=parsed_add_arch_template_vars,
               remove_temp=True, verify=opts.verify,
-              user_dracut_args=opts.dracut_args)
+              user_dracut_args=opts.dracut_args,
+              squashfs_only=opts.squashfs_only)
 
 
 def get_dnf_base_object(installroot, sources, mirrorlists=None, repos=None,