From f641455c06f18da52bf7fd9c5228d6e3c5ce1453 Mon Sep 17 00:00:00 2001
From: "Owen W. Taylor" <otaylor@fishsoup.net>
Date: Fri, 20 Oct 2023 11:26:17 -0400
Subject: [PATCH] Docker.py: Pass the use_ino option to fix hardlnks
When use libguestfs to mount the intermediate image to create a tarball,
pass the "use_ino" option so that original inode numbers are preserved.
This fixes a problem where hardlinks were not properly preserved in the
output.
This is a minimal-code-change fix - an edge case bug and better approach are
described in comments.
Resolves #412
---
imagefactory_plugins/Docker/Docker.py | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/imagefactory_plugins/Docker/Docker.py b/imagefactory_plugins/Docker/Docker.py
index 68e12c3926bb..960b0e43325c 100644
--- a/imagefactory_plugins/Docker/Docker.py
+++ b/imagefactory_plugins/Docker/Docker.py
@@ -312,12 +312,32 @@ class Docker(object):
# we call a blocking function to activate the mount, which requires a thread
# We also need a temp dir to mount it to - do our best to clean up when things
# go wrong
+ #
+ # A better approach here would be to use:
+ # g.tar_out_opts("/", dest_filename, excludes=[excludes])
+ # Though that would break compatibility with the tar_options parameter.
+ #
tempdir = None
fuse_thread = None
try:
tempdir = tempfile.mkdtemp(dir=storagedir)
self.log.debug("Mounting input image locally at (%s)" % (tempdir))
- guestfs_handle.mount_local(tempdir)
+
+ # The "use_ino" option causes FUSE to pass through the original inode
+ # numbers. Without it tar cannot properly detect hardlinks, possibly greatly
+ # increasing the size of the image. This does create an edge case. If there
+ # are:
+ #
+ # - Two separate groups of > 1 files hardlinked together
+ # - On different partitions
+ # - With the same inode number
+ #
+ # Then the groups will be incorrectly merged in the output image. This
+ # is unlikely to be encountered with typical container images, where almost
+ # all files are on a single partition. The correct fix is to use
+ # g.tar_out_opts() as described above.
+
+ guestfs_handle.mount_local(tempdir, options="use_ino")
def _run_guestmount(g):
g.mount_local_run()
self.log.debug("Launching mount_local_run thread")
--
2.41.0