buildah: Rootless user can't build modified image based on Shared Image

I created a shared OCI image using the instructions in this great article (https://www.redhat.com/sysadmin/image-stores-podman). This works well for starting containers based on a shared image. However, it seems that when a rootless user tries to create a new image based on an image in the shared area, and makes any changes as part of building the new image, this will trigger an error similar to the following.

error copying layers and metadata for container "ec75ba443567a5d2673f54474704b3198c9e7a820d7bc83c3e1dbf653326006b": Error initializing source containers-storage:fedora-working-container: error extracting layer "e27dcbf8b9e467a69b5f1d9cae79f91a70c1845714f1adf154d38580f4eb16d7": chown /var/lib/mycontainers/overlay/0203e243f1ca4b6bb49371ecd21363212467ec6d7d3fa9f324cd4e78cc6b5fa2/diff: operation not permitted

This seems to suggest that buildah is trying to make changes in the read only shared directory?

Notes.

• These steps work without issue for root user, or if the Dockerfile shown in step 6. below does not include the COPY line.
• I’ve noticed that closed issues 2161 and 2359 are somewhat similar, but don’t exactly match the symptoms or error

Steps to reproduce the issue:

1. Create intended shared image directory as root mkdir /var/lib/mycontainers

2. Pull fedora image using --root option # podman --root /var/lib/mycontainers pull fedora

3. Ensure shared directory contents are world-readable sudo chmod -R a+rx /var/lib/mycontainers

4. Confirm non-root user “support” set up for rootless access [root@localhost github_2161_exper]# cat /etc/subuid support:100000:65536 user1:165536:65536 [root@localhost github_2161_exper]# cat /etc/subgid support:100000:65536 user1:165536:65536

5. Create a text file, to be added to newly created image (just to represent any change to image) [support@localhost github_2161_exper]$ cat this.txt thistext

6. As non-root user, create Dockerfile to clone and modify fedora image [support@localhost [github_2161_exper]$ cat Dockerfile_fedora_withCOPY FROM registry.fedoraproject.org/fedora:latest as build-env COPY this.txt /tmp/this.txt

6.5. (Edit Oct 13 '21 - missed this step when originally posting bug) Create storage.conf in rootless user’s home directory with: $ cat ~/.config/containers/storage.conf [storage] driver = "overlay" [storage.options] additionalimagestores = [ "/var/lib/mycontainers",] [storage.options.overlay] mount_program = "/usr/bin/fuse-overlayfs"

1. Run Dockerfile [support@localhost github_2161_exper]$ podman build -t fedora_fr_podman:latest -f Dockerfile_fedora_withCOPY

Describe the results you received:

STEP 1: FROM registry.fedoraproject.org/fedora:latest AS build-env STEP 2: COPY this.txt /tmp/this.txt STEP 3: COMMIT fedora_fr_podman:latest Error: error committing container for step {Env:[DISTTAG=f34container FGC=f34 container=oci PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin] Command:copy Args:[this.txt /tmp/this.txt] Flags:[] Attrs:map[] Message:COPY this.txt /tmp/this.txt Original:COPY this.txt /tmp/this.txt}: error copying layers and metadata for container "ec75ba443567a5d2673f54474704b3198c9e7a820d7bc83c3e1dbf653326006b": Error initializing source containers-storage:fedora-working-container: error extracting layer "e27dcbf8b9e467a69b5f1d9cae79f91a70c1845714f1adf154d38580f4eb16d7": chown /var/lib/mycontainers/overlay/0203e243f1ca4b6bb49371ecd21363212467ec6d7d3fa9f324cd4e78cc6b5fa2/diff: operation not permitted

Describe the results you expected:

New image created successfully

Output of rpm -q buildah or apt list buildah:

[support@localhost github_2161_exper]$ rpm -q buildah
buildah-1.21.4-1.module+el8.4.0+11989+6676f7ad.x86_64

Output of buildah version:

[support@localhost github_2161_exper]$ buildah version
Version:         1.21.4
Go Version:      go1.15.7
Image Spec:      1.0.1-dev
Runtime Spec:    1.0.2-dev
CNI Spec:        0.4.0
libcni Version:  v0.8.1
image Version:   5.12.0
Git Commit:      
Built:           Tue Jul 27 03:29:47 2021
OS/Arch:         linux/amd64

Output of podman version if reporting a podman build issue:

[support@localhost github_2161_exper]$ podman version
Version:      3.2.3
API Version:  3.2.3
Go Version:   go1.15.7
Built:        Tue Jul 27 03:29:39 2021
OS/Arch:      linux/amd64

Output of cat /etc/*release:

NAME="Red Hat Enterprise Linux"
VERSION="8.4 (Ootpa)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="8.4"
PLATFORM_ID="platform:el8"
PRETTY_NAME="Red Hat Enterprise Linux 8.4 (Ootpa)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:8.4:GA"
HOME_URL="https://www.redhat.com/"
DOCUMENTATION_URL="https://access.redhat.com/documentation/red_hat_enterprise_linux/8/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"

REDHAT_BUGZILLA_PRODUCT="Red Hat Enterprise Linux 8"
REDHAT_BUGZILLA_PRODUCT_VERSION=8.4
REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux"
REDHAT_SUPPORT_PRODUCT_VERSION="8.4"
Red Hat Enterprise Linux release 8.4 (Ootpa)
Red Hat Enterprise Linux release 8.4 (Ootpa)

Output of uname -a:

Linux localhost.localdomain 4.18.0-305.19.1.el8_4.x86_64 #1 SMP Tue Sep 7 07:07:31 EDT 2021 x86_64 x86_64 x86_64 GNU/Linux

Output of cat /etc/containers/storage.conf:

# This file is is the configuration file for all tools
# that use the containers/storage library.
# 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
graphroot = "/var/lib/containers/storage"

# Storage path for rootless users
#
# rootless_storage_path = "$HOME/.local/share/containers/storage"

[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 = [
]

# 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.
#
# 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 minimum 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"

# 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"

# 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 then the
#  "force_mask"  permissions.
#
# force_mask = ""

[storage.options.thinpool]
# Storage Options for thinpool

# autoextend_percent determines the amount by which pool needs to be
# grown. This is specified in terms of % of pool size. So a value of 20 means
# that when threshold is hit, pool will be grown by 20% of existing
# pool size.
# autoextend_percent = "20"

# autoextend_threshold determines the pool extension threshold in terms
# of percentage of pool size. For example, if threshold is 60, that means when
# pool is 60% full, threshold has been hit.
# autoextend_threshold = "80"

# basesize specifies the size to use when creating the base device, which
# limits the size of images and containers.
# basesize = "10G"

# blocksize specifies a custom blocksize to use for the thin pool.
# blocksize="64k"

# directlvm_device specifies a custom block storage device to use for the
# thin pool. Required if you setup devicemapper.
# directlvm_device = ""

# directlvm_device_force wipes device even if device already has a filesystem.
# directlvm_device_force = "True"

# fs specifies the filesystem type to use for the base device.
# fs="xfs"

# log_level sets the log level of devicemapper.
# 0: LogLevelSuppress 0 (Default)
# 2: LogLevelFatal
# 3: LogLevelErr
# 4: LogLevelWarn
# 5: LogLevelNotice
# 6: LogLevelInfo
# 7: LogLevelDebug
# log_level = "7"

# min_free_space specifies the min free space percent in a thin pool require for
# new device creation to succeed. Valid values are from 0% - 99%.
# Value 0% disables
# min_free_space = "10%"

# mkfsarg specifies extra mkfs arguments to be used when creating the base
# device.
# mkfsarg = ""

# metadata_size is used to set the `pvcreate --metadatasize` options when
# creating thin devices. Default is 128k
# metadata_size = ""

# Size is used to set a maximum size of the container image.
# size = ""

# use_deferred_removal marks devicemapper block device for deferred removal.
# If the thinpool is in use when the driver attempts to remove it, the driver
# tells the kernel to remove it as soon as possible. Note this does not free
# up the disk space, use deferred deletion to fully remove the thinpool.
# use_deferred_removal = "True"

# use_deferred_deletion marks thinpool device for deferred deletion.
# If the device is busy when the driver attempts to delete it, the driver
# will attempt to delete device every 30 seconds until successful.
# If the program using the driver exits, the driver will continue attempting
# to cleanup the next time the driver is used. Deferred deletion permanently
# deletes the device and all data stored in device will be lost.
# use_deferred_deletion = "True"

# xfs_nospace_max_retries specifies the maximum number of retries XFS should
# attempt to complete IO when ENOSPC (no space) error is returned by
# underlying storage device.
# xfs_nospace_max_retries = "0"

Output of rootless user’s storage.conf - cat ~/.config/containers/storage.conf:

[storage] driver = “overlay” [storage.options] additionalimagestores = [ “/var/lib/mycontainers”,] [storage.options.overlay] mount_program = “/usr/bin/fuse-overlayfs”`