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Description
Issue Description
When a layer contains multiple hardlinks pointing to the same file, e.g.
tmp/end
tmp/link1 link to tmp/end
tmp/link10 link to tmp/end
tmp/link2 link to tmp/end
tmp/link3 link to tmp/end
tmp/link4 link to tmp/end
tmp/link5 link to tmp/end
tmp/link6 link to tmp/end
tmp/link7 link to tmp/end
tmp/link8 link to tmp/end
tmp/link9 link to tmp/end
In version v1.40.1, the above is how they're represented in the layer - they each link directly to the target file.
But in version v1.41.0, they are instead represented like this:
tmp/end
tmp/link1 link to tmp/end
tmp/link10 link to tmp/link1
tmp/link2 link to tmp/link10
tmp/link3 link to tmp/link2
tmp/link4 link to tmp/link3
tmp/link5 link to tmp/link4
tmp/link6 link to tmp/link5
tmp/link7 link to tmp/link6
tmp/link8 link to tmp/link7
tmp/link9 link to tmp/link8
Each hardlink points to the hardlink that alphabetically precedes it (until the first one, which links to the actual file).
This has two effects that I know of.
- If someone is using the
--timestamp
argument to pursue bitwise reproducibility, layers that would have identical digests in prior buildah versions will now have a different digest - Image scanning tools that extract files directly from layers have to follow a linked list of hardlinks to get to the actual file. The reason why we even noticed this problem is that we run
syft
on images and gotmaximum link resolution stack depth exceeded
on an image with a lot of hardlinks pointing to/usr/bin/git
Steps to reproduce the issue
Steps to reproduce the issue
- Compile buildah at the v1.40.1 tag
cat << 'EOF' > Containerfile.test
FROM registry.fedoraproject.org/fedora-minimal:42@sha256:ec351a5a23b04fbef7ebf2d0440be4239b2925abbfc05c506dcb88a064ccd363
RUN touch /tmp/end && \
for i in {1..10}; do ln /tmp/end /tmp/link${i}; done
EOF
bin/buildah build --no-cache --timestamp 1753375945 -t test:latest -f Containerfile.test
bin/buildah push test:latest oci:v1.40.1.dir
tar tvf v1.40.1.dir/blobs/sha256/6f5be6765945588f1e5c1358538b543c443c17d75d4708993d4d8433c52421df
# drwxr-xr-x 0/0 0 2025-07-24 18:52 etc/
# -rwx------ 0/0 0 2025-07-24 18:52 etc/hostname
# -rwx------ 0/0 0 2025-07-24 18:52 etc/resolv.conf
# drwxr-xr-x 0/0 0 2025-07-24 18:52 run/
# drwxrwxrwt 0/0 0 2025-07-24 18:52 tmp/
# -rw-r--r-- 0/0 0 2025-07-24 18:52 tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link1 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link10 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link2 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link3 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link4 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link5 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link6 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link7 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link8 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link9 link to tmp/end
- Compile buildah at the v1.41.0 tag
bin/buildah build --no-cache --timestamp 1753375945 -t test:latest -f Containerfile.test
bin/buildah push test:latest oci:v1.41.0.dir
tar tvf v1.41.0.dir/blobs/sha256/6f83ea355581ba4adddda193cb33644c4cfee5d1f8cbf087e997a9be35035638
# drwxr-xr-x 0/0 0 2025-07-24 18:52 dev/
# drwxr-xr-x 0/0 0 2025-07-24 18:52 etc/
# drwxr-xr-x 0/0 0 2025-07-24 18:52 run/
# drwxrwxrwt 0/0 0 2025-07-24 18:52 tmp/
# -rw-r--r-- 0/0 0 2025-07-24 18:52 tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link1 link to tmp/end
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link10 link to tmp/link1
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link2 link to tmp/link10
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link3 link to tmp/link2
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link4 link to tmp/link3
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link5 link to tmp/link4
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link6 link to tmp/link5
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link7 link to tmp/link6
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link8 link to tmp/link7
# hrw-r--r-- 0/0 0 2025-07-24 18:52 tmp/link9 link to tmp/link8
Describe the results you received
In v1.41.0, hardlinks in layers make up a linked list where each hardlink points to the one that alphabetically precedes it
Describe the results you expected
Expected the layout to be the same as in v1.40.1, where hardlinks point directly to the target file
buildah version output
Version: 1.41.0
Go Version: go1.24.5
Image Spec: 1.1.1
Runtime Spec: 1.2.1
CNI Spec: 1.1.0
libcni Version: v1.3.0
image Version: 5.36.0
Git Commit: 9f185b7777df7aa9c032911f823c39aa724b5707
Built: Thu Jul 24 19:23:30 2025
OS/Arch: linux/amd64
BuildPlatform: linux/amd64
buildah info output
{
"host": {
"CgroupVersion": "v2",
"Distribution": {
"distribution": "fedora",
"version": "42"
},
"MemFree": 2648797184,
"MemTotal": 33058652160,
"OCIRuntime": "crun",
"SwapFree": 6906081280,
"SwapTotal": 8589930496,
"arch": "amd64",
"cpus": 14,
"hostname": "acmiel-thinkpadx1carbongen12.tpbc.csb",
"kernel": "6.15.4-200.fc42.x86_64",
"os": "linux",
"rootless": true,
"uptime": "82h 17m 9.36s (Approximately 3.42 days)",
"variant": ""
},
"store": {
"ContainerStore": {
"number": 120
},
"GraphDriverName": "overlay",
"GraphOptions": null,
"GraphRoot": "/home/acmiel/.local/share/containers/storage",
"GraphStatus": {
"Backing Filesystem": "btrfs",
"Native Overlay Diff": "true",
"Supports d_type": "true",
"Supports shifting": "false",
"Supports volatile": "true",
"Using metacopy": "false"
},
"ImageStore": {
"number": 215
},
"RunRoot": "/run/user/105500/containers"
}
}
Provide your storage.conf
# This file is the configuration file for all tools
# that use the containers/storage library. The storage.conf file
# overrides all other storage.conf files. Container engines using the
# container/storage library do not inherit fields from other storage.conf
# files.
#
# Note: The storage.conf file overrides other storage.conf files based on this precedence:
# /usr/containers/storage.conf
# /etc/containers/storage.conf
# $HOME/.config/containers/storage.conf
# $XDG_CONFIG_HOME/containers/storage.conf (If XDG_CONFIG_HOME is set)
# See man 5 containers-storage.conf for more information
# The "container storage" table contains all of the server options.
[storage]
# Default Storage Driver, Must be set for proper operation.
driver = "overlay"
# Temporary storage location
runroot = "/run/containers/storage"
# Primary Read/Write location of container storage
# When changing the graphroot location on an SELINUX system, you must
# ensure the labeling matches the default locations labels with the
# following commands:
# semanage fcontext -a -e /var/lib/containers/storage /NEWSTORAGEPATH
# restorecon -R -v /NEWSTORAGEPATH
graphroot = "/var/lib/containers/storage"
# Optional alternate location of image store if a location separate from the
# container store is required. If set, it must be different than graphroot.
# imagestore = ""
# Storage path for rootless users
#
# rootless_storage_path = "$HOME/.local/share/containers/storage"
# Transient store mode makes all container metadata be saved in temporary storage
# (i.e. runroot above). This is faster, but doesn't persist across reboots.
# Additional garbage collection must also be performed at boot-time, so this
# option should remain disabled in most configurations.
# transient_store = true
[storage.options]
# Storage options to be passed to underlying storage drivers
# AdditionalImageStores is used to pass paths to additional Read/Only image stores
# Must be comma separated list.
additionalimagestores = [
"/usr/lib/containers/storage",
]
# Allows specification of how storage is populated when pulling images. This
# option can speed the pulling process of images compressed with format
# zstd:chunked. Containers/storage looks for files within images that are being
# pulled from a container registry that were previously pulled to the host. It
# can copy or create a hard link to the existing file when it finds them,
# eliminating the need to pull them from the container registry. These options
# can deduplicate pulling of content, disk storage of content and can allow the
# kernel to use less memory when running containers.
# containers/storage supports four keys
# * enable_partial_images="true" | "false"
# Tells containers/storage to look for files previously pulled in storage
# rather then always pulling them from the container registry.
# * use_hard_links = "false" | "true"
# Tells containers/storage to use hard links rather then create new files in
# the image, if an identical file already existed in storage.
# * ostree_repos = ""
# Tells containers/storage where an ostree repository exists that might have
# previously pulled content which can be used when attempting to avoid
# pulling content from the container registry
# * convert_images = "false" | "true"
# If set to true, containers/storage will convert images to a
# format compatible with partial pulls in order to take advantage
# of local deduplication and hard linking. It is an expensive
# operation so it is not enabled by default.
pull_options = {enable_partial_images = "true", use_hard_links = "false", ostree_repos=""}
# Remap-UIDs/GIDs is the mapping from UIDs/GIDs as they should appear inside of
# a container, to the UIDs/GIDs as they should appear outside of the container,
# and the length of the range of UIDs/GIDs. Additional mapped sets can be
# listed and will be heeded by libraries, but there are limits to the number of
# mappings which the kernel will allow when you later attempt to run a
# container.
#
# remap-uids = "0:1668442479:65536"
# remap-gids = "0:1668442479:65536"
# Remap-User/Group is a user name which can be used to look up one or more UID/GID
# ranges in the /etc/subuid or /etc/subgid file. Mappings are set up starting
# with an in-container ID of 0 and then a host-level ID taken from the lowest
# range that matches the specified name, and using the length of that range.
# Additional ranges are then assigned, using the ranges which specify the
# lowest host-level IDs first, to the lowest not-yet-mapped in-container ID,
# until all of the entries have been used for maps. This setting overrides the
# Remap-UIDs/GIDs setting.
#
# remap-user = "containers"
# remap-group = "containers"
# Root-auto-userns-user is a user name which can be used to look up one or more UID/GID
# ranges in the /etc/subuid and /etc/subgid file. These ranges will be partitioned
# to containers configured to create automatically a user namespace. Containers
# configured to automatically create a user namespace can still overlap with containers
# having an explicit mapping set.
# This setting is ignored when running as rootless.
# root-auto-userns-user = "storage"
#
# Auto-userns-min-size is the minimum size for a user namespace created automatically.
# auto-userns-min-size=1024
#
# Auto-userns-max-size is the maximum size for a user namespace created automatically.
# auto-userns-max-size=65536
[storage.options.overlay]
# ignore_chown_errors can be set to allow a non privileged user running with
# a single UID within a user namespace to run containers. The user can pull
# and use any image even those with multiple uids. Note multiple UIDs will be
# squashed down to the default uid in the container. These images will have no
# separation between the users in the container. Only supported for the overlay
# and vfs drivers.
#ignore_chown_errors = "false"
# Inodes is used to set a maximum inodes of the container image.
# inodes = ""
# Path to an helper program to use for mounting the file system instead of mounting it
# directly.
#mount_program = "/usr/bin/fuse-overlayfs"
# mountopt specifies comma separated list of extra mount options
mountopt = "nodev,metacopy=on"
# Set to skip a PRIVATE bind mount on the storage home directory.
# skip_mount_home = "false"
# Set to use composefs to mount data layers with overlay.
# use_composefs = "false"
# Size is used to set a maximum size of the container image.
# size = ""
# ForceMask specifies the permissions mask that is used for new files and
# directories.
#
# The values "shared" and "private" are accepted.
# Octal permission masks are also accepted.
#
# "": No value specified.
# All files/directories, get set with the permissions identified within the
# image.
# "private": it is equivalent to 0700.
# All files/directories get set with 0700 permissions. The owner has rwx
# access to the files. No other users on the system can access the files.
# This setting could be used with networked based homedirs.
# "shared": it is equivalent to 0755.
# The owner has rwx access to the files and everyone else can read, access
# and execute them. This setting is useful for sharing containers storage
# with other users. For instance have a storage owned by root but shared
# to rootless users as an additional store.
# NOTE: All files within the image are made readable and executable by any
# user on the system. Even /etc/shadow within your image is now readable by
# any user.
#
# OCTAL: Users can experiment with other OCTAL Permissions.
#
# Note: The force_mask Flag is an experimental feature, it could change in the
# future. When "force_mask" is set the original permission mask is stored in
# the "user.containers.override_stat" xattr and the "mount_program" option must
# be specified. Mount programs like "/usr/bin/fuse-overlayfs" present the
# extended attribute permissions to processes within containers rather than the
# "force_mask" permissions.
#
# force_mask = ""
Upstream Latest Release
Yes
Additional environment details
No response
Additional information
If I bisected correctly, then the commit that introduced the change is 5b26b79