Unprivileged buildah bud in Kube: Overlay fails, but vfs does not

[johnmcollier]

Description

I'm running the buildah docker image (quay.io/buildah/stable:v1.11.3) in Kubernetes (OCP 4.2) as root, but unprivileged. When I go to build a sample application, the build fails with the following error:

sh-5.0# buildah bud -t test .
STEP 1: FROM golang:latest
Getting image source signatures
Copying blob d918eaefd9de done
Copying blob 8f0fdd3eaac0 done
Copying blob 410143ccff32 done
Copying blob f862a94ee651 done
Copying blob 43bf3e3107f5 done
Copying blob 27622921edb2 done
Copying blob 4e820fb4177f done
Copying config 272e3f6833 done
Writing manifest to image destination
Storing signatures
ERRO error unmounting /var/lib/containers/storage/overlay/5e69c48334b8272f41883e53d07ad011bd609f9fe3f40803c685901e579afc4f/merged: invalid argument 
error mounting new container: error mounting build container "2eb93270c9036f7f6fb335b6882d7b9268c20f453cb70121cc727f8580ce698e": error creating overlay mount to /var/lib/containers/storage/overlay/5e69c48334b8272f41883e53d07ad011bd609f9fe3f40803c685901e579afc4f/merged: using mount program /usr/bin/fuse-overlayfs: fuse: device not found, try 'modprobe fuse' first
fuse-overlayfs: cannot mount: No such file or directory
: exit status 1
ERRO exit status 1                                

If I build with buildah --storage-driver vfs bud, it does not fail:

sh-5.0# buildah --storage-driver vfs bud -t test .
STEP 1: FROM golang:latest
STEP 2: RUN mkdir /app 
STEP 3: ADD . /app/ 
STEP 4: WORKDIR /app 
STEP 5: RUN go build -o main . 
STEP 6: CMD ["/app/main"]
STEP 7: EXPOSE 8000
STEP 8: COMMIT test
Getting image source signatures
Copying blob dd5242c2dc8a skipped: already exists
Copying blob 6f1c84e6ec59 skipped: already exists
Copying blob b52c1c103fae skipped: already exists
Copying blob e6d60910d056 skipped: already exists
Copying blob 3d6d182dab88 skipped: already exists
Copying blob efdff2422869 skipped: already exists
Copying blob e5abe1112ca1 skipped: already exists
Copying blob a5e1d10e436c done
Copying config 585b37e422 done
Writing manifest to image destination
Storing signatures
585b37e422e742838072b762854a02961250c2c64ba8a8a7fd35c72753c3dd71

It might be because I can't mount /dev/fuse on Kubernetes? (https://github.com/kubernetes/kubernetes/issues/5607#issuecomment-414663936). Is there any way around that?

Steps to reproduce the issue:

1. Run the official buildah docker image on Kubernetes. Don't run it as privileged
2. Git clone the sample project here: https://github.com/johnmcollier/gopushtest
3. Run buildah bud -t <tag> .. The build will fail. But buildah --storage-driver vfs -t <tag> . works fine

Describe the results you received: Buildah bud in Kube fails with overlay.

Describe the results you expected: Buildah bud in Kube with overlay works.

Output of rpm -q buildah or apt list buildah:

buildah-1.11.3-2.fc30.x86_64

Output of buildah version:

sh-5.0# buildah version
Version:         1.11.3
Go Version:      go1.12.9
Image Spec:      1.0.1-dev
Runtime Spec:    1.0.1-dev
CNI Spec:        0.4.0
libcni Version:  
Git Commit:      
Built:           Thu Jan  1 00:00:00 1970
OS/Arch:         linux/amd64

*Output of `cat /etc/release`:**

sh-5.0# cat /etc/*release
Fedora release 30 (Thirty)
NAME=Fedora
VERSION="30 (Container Image)"
ID=fedora
VERSION_ID=30
VERSION_CODENAME=""
PLATFORM_ID="platform:f30"
PRETTY_NAME="Fedora 30 (Container Image)"
ANSI_COLOR="0;34"
LOGO=fedora-logo-icon
CPE_NAME="cpe:/o:fedoraproject:fedora:30"
HOME_URL="https://fedoraproject.org/"
DOCUMENTATION_URL="https://docs.fedoraproject.org/en-US/fedora/f30/system-administrators-guide/"
SUPPORT_URL="https://fedoraproject.org/wiki/Communicating_and_getting_help"
BUG_REPORT_URL="https://bugzilla.redhat.com/"
REDHAT_BUGZILLA_PRODUCT="Fedora"
REDHAT_BUGZILLA_PRODUCT_VERSION=30
REDHAT_SUPPORT_PRODUCT="Fedora"
REDHAT_SUPPORT_PRODUCT_VERSION=30
PRIVACY_POLICY_URL="https://fedoraproject.org/wiki/Legal:PrivacyPolicy"
VARIANT="Container Image"
VARIANT_ID=container
Fedora release 30 (Thirty)
Fedora release 30 (Thirty)

Output of uname -a:

sh-5.0# uname -a
Linux codewind-pfe-k5cpsqyz-8678cbbb66-f44jn 4.18.0-80.11.2.el8_0.x86_64 #1 SMP Sun Sep 15 11:24:21 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

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

sh-5.0# 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
driver = "overlay"

# Temporary storage location
runroot = "/var/run/containers/storage"

# Primary Read/Write location of container storage
graphroot = "/var/lib/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 = [
"/var/lib/shared",
]

# Size is used to set a maximum size of the container image.  Only supported by
# certain container storage drivers.
size = ""

# Path to an helper program to use for mounting the file system instead of mounting it
# directly.
mount_program = "/usr/bin/fuse-overlayfs"

# OverrideKernelCheck tells the driver to ignore kernel checks based on kernel version
override_kernel_check = "true"

# mountopt specifies comma separated list of extra mount options
mountopt = "nodev,metacopy=on"

# Remap-UIDs/GIDs is the mapping from UIDs/GIDs as they should appear inside of
# a container, to 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 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 the 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 container-level ID,
# until all of the entries have been used for maps.
#
# remap-user = "storage"
# remap-group = "storage"

[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 = ""

# 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"

# If specified, use OSTree to deduplicate files with the overlay backend
ostree_repo = ""

# Set to skip a PRIVATE bind mount on the storage home directory.  Only supported by
# certain container storage drivers
skip_mount_home = "false"

[smothiki]

I'm also facing the same issue. is there any workaround to use overlay in unprivileged mode ?

[rhatdan]

Did you try with the quay.io/buildah/stable image? Note you need to run with --device /dev/fuse

[johnmcollier]

Yup, I was using an image based off of that.

I can’t pass in the —device flag when running on Kube, as Kube doesn’t support mounting devices

[rhatdan]

In crio you can add this device to all containers, Something I think we should do by default.

[smothiki]

@rhatdan we have added devfuse in crio config

additional_devices = [
  "/dev/fuse:/dev/fuse:rwm",
]

Now all the containers are having fuse device added but still getting the same error.

error mounting new container: error mounting build container "6f17a2a37df4352dc6a08bfbac27d3464a7a38e9d7919c47652854f36be4094e": error creating overlay mount to /var/lib/containers/storage/overlay/be6fb89e2de7c93593f090fe3ba231d07695315b60e38cd561d11792009caa06/merged: using mount program /usr/bin/fuse-overlayfs: fuse: device not found, try 'modprobe fuse' first

[rhatdan]

@umohnani8 @haircommander PTAL

[rhatdan]

@smothiki You might need to mod fuse on the host. I wonder if this device even exists on the cri-o node.

[smothiki]

Okay did modprobe fuse in the host and it worked in the container