IMG-独立的支持OCI的容器镜像构建工具
Standalone, daemon-less, unprivileged Dockerfile and OCI compatible container image builder.
img is more cache-efficient than Docker and can also execute multiple build stages concurrently, as it internally uses BuildKit's DAG solver.
The commands/UX are the same as docker {build,push,pull,login} so all you have to do is replace docker with img in your scripts, command line, and/or life.
Currently you can run it as unprivileged if you follow the instructions in the unprivileged mounting section below.
You might also be interested in reading the original design doc.
Snapshotter Backends
The default backend is currently set to naive and requires privileges, but it can be made unprivileged and that work is being done, see the unprivileged mounting section below. It is a lot more stable than the fuse backend. You can also use overlayfs backend, but that requires a kernel patch from Ubuntu to be unprivileged, see #22.
The fuse backend runs completely in userspace. It is a bit buggy and a work in progress so hang tight.
Unprivileged Mounting
To mount a filesystem without root access you need to do it from a mount and user namespace.
Make sure you have user namespace support enabled. On some distros (Debian and Arch Linux) this requires running echo 1 > /proc/sys/kernel/unprivileged_userns_clone.
You also need a version of runc with the patches from opencontainers/runc#1688.
Example:
# unshare a mountns and userns # and remap the user inside the namespaces to your current user $ unshare -m -U --map-root-user # then you can run img $ img build -t user/myimage .
Note that unshare -m -U --map-root-user does not make use of subuid(5)/subgid(5), and also, it disables setgroups(2), which is typically required by apt.
So we might want to use newuidmap(1)/newgidmap(1) SUID binaries to enable these features. See opencontainers/runc#1692 and opencontainers/runc#1693.
If depending on these SUID binaries is problematic, we could use ptrace hacks such as PRoot, although its performance overhead is not negligible. (#15 and AkihiroSuda/runrootless)
For the on-going work toward integrating runc with these patches to buildkit, please refer to moby/buildkit#252 and AkihiroSuda/buildkit_poc@511c7e71.
Goals
This project is not trying to reinvent buildkit. If anything all changes and modifications for buildkit without privileges are being done upstream. The goal of this project is to in the future just be a glorified cli tool on top of buildkit.
Table of Contents
Installation
You need to have runc installed.
For the FUSE backend, you will also need fusermount installed.
Binaries
- linux amd64
Via Go
$ go get github.com/jessfraz/img
NOTE: Only works on Linux. Compile and run in a container (explained below) if you're on Windows or MacOS ;)
Running with Docker
$ docker run --rm -it \
--name img \
--volume /place/for/my/state:/tmp/img \ # for the builder state
--volume $(pwd):/src:ro \ # for the build context and dockerfile, can be read-only since we won't modify it
--workdir /src \ # set the builder working directory
--volume "${HOME}/.docker:/root/.docker:ro" \ # for credentials to push to docker hub or a registry
--cap-add SYS_ADMIN \ # so we can mount if we aren't running as unprivileged
--security-opt apparmor=unconfined \ # turn off apparmor so we can mount
--security-opt seccomp=unconfined \ # turn off seccomp so the runc children can use the kernel keyring
--volume /sys/fs/cgroup:/sys/fs/cgroup \ # so we can have nested cgroups for the runc build containers
r.j3ss.co/img build -t user/myimage .
Usage
$ img -h Usage: img <command> Commands: build Build an image from a Dockerfile. du Show image disk usage. ls List images and digests. login Log in to a Docker registry. pull Pull an image or a repository from a registry. push Push an image or a repository to a registry. tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE. version Show the version information.
Build an Image
$ img build -h Usage: img build [OPTIONS] PATH Build an image from a Dockerfile. Flags: -backend backend for snapshots ([fuse naive overlayfs]) (default: naive) -build-arg Set build-time variables (default: []) -d enable debug logging (default: false) -f Name of the Dockerfile (Default is 'PATH/Dockerfile') (default: <none>) -state directory to hold the global state (default: /tmp/img) -t Name and optionally a tag in the 'name:tag' format (default: <none>) -target Set the target build stage to build (default: <none>)
Use just like you would docker build.
$ sudo img build -t jess/img . Building jess/img Setting up the rootfs... this may take a bit. RUN [/bin/sh -c apk add --no-cache ca-certificates] ---> fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz OK: 5 MiB in 12 packages <--- 5e433zdbh8eosea0u9b70axb3 0 <nil> RUN [copy /src-0 /dest/go/src/github.com/jessfraz/img] ---> <--- rqku3imaivvjpgl676se1gupc 0 <nil> RUN [/bin/sh -c set -x && apk add --no-cache --virtual .build-deps bash git gcc libc-dev libgcc libseccomp-dev linux-headers make && cd /go/src/github.com/jessfraz/img && make static && mv img /usr/bin/img && mkdir -p /go/src/github.com/opencontainers && git clone https://github.com/opencontainers/runc /go/src/github.com/opencontainers/runc && cd /go/src/github.com/opencontainers/runc && make static BUILDTAGS="seccomp" EXTRA_FLAGS="-buildmode pie" EXTRA_LDFLAGS="-extldflags \\\"-fno-PIC -static\\\"" && mv runc /usr/bin/runc && apk del .build-deps && rm -rf /go && echo "Build complete."] ---> + apk add --no-cache --virtual .build-deps bash git gcc libc-dev libgcc libseccomp-dev linux-headers make fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz (1/28) Installing pkgconf (1.3.10-r0) (2/28) Installing ncurses-terminfo-base (6.0_p20171125-r0) (3/28) Installing ncurses-terminfo (6.0_p20171125-r0) (4/28) Installing ncurses-libs (6.0_p20171125-r0) (5/28) Installing readline (7.0.003-r0) (6/28) Installing bash (4.4.19-r1) .... .... RUN [copy /src-0/certs /dest/etc/ssl/certs] ---> <--- 6ljir2x800w6deqlradhw0dy2 0 <nil> Successfully built jess/img
List Image Layers
$ img ls -h Usage: img ls [OPTIONS] List images and digests. Flags: -backend backend for snapshots ([fuse naive overlayfs]) (default: naive) -d enable debug logging (default: false) -f Filter output based on conditions provided (default: []) -state directory to hold the global state (default: /tmp/img)
$ img ls --backend=fuse NAME SIZE CREATED AT UPDATED AT DIGEST jess/img:latest 1.534KiB 9 seconds ago 9 seconds ago sha256:27d862ac32022946d61afbb91ddfc6a1fa2341a78a0da11ff9595a85f651d51e jess/thing:latest 591B 30 minutes ago 30 minutes ago sha256:d664b4e9b9cd8b3067e122ef68180e95dd4494fd4cb01d05632b6e77ce19118e
Pull an Image
$ img pull -h Usage: img pull [OPTIONS] NAME[:TAG|@DIGEST] Pull an image or a repository from a registry. Flags: -backend backend for snapshots ([fuse naive overlayfs]) (default: naive) -d enable debug logging (default: false) -state directory to hold the global state (default: /tmp/img)
$ img pull --backend=fuse r.j3ss.co/stress Pulling r.j3ss.co/stress:latest... Snapshot ref: sha256:2bb7a0a5f074ffe898b1ef64b3761e7f5062c3bdfe9947960e6db48a998ae1d6 Size: 365.9KiB
Push an Image
$ img push -h Usage: img push [OPTIONS] NAME[:TAG] Push an image or a repository to a registry. Flags: -backend backend for snapshots ([fuse naive overlayfs]) (default: naive) -d enable debug logging (default: false) -state directory to hold the global state (default: /tmp/img)
$ img push --backend=fuse jess/thing Pushing jess/thing:latest... Successfully pushed jess/thing:latest
Tag an Image
$ img tag -h Usage: img tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG] Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE. Flags: -backend backend for snapshots ([fuse naive overlayfs]) (default: naive) -d enable debug logging (default: false) -state directory to hold the global state (default: /tmp/img)
$ img tag jess/thing jess/otherthing Successfully tagged jess/thing as jess/otherthing
Disk Usage
$ img du -h Usage: img du [OPTIONS] Show image disk usage. Flags: -backend backend for snapshots ([fuse naive overlayfs]) (default: naive) -d enable debug logging (default: false) -f Filter output based on conditions provided (snapshot ID supported) (default: <none>) -state directory to hold the global state (default: /tmp/img)
$ img du --backend=fuse ID RECLAIMABLE SIZE DESCRIPTION sha256:d9a48086f223d28a838263a6c04705c8009fab1dd67cc82c0ee821545de3bf7c true 911.8KiB pulled from docker.io/tonistiigi/copy@sha256:476e0a67a1e4650c6adaf213269a2913deb7c52cbc77f954026f769d51e1a14e 7ia86xm2e4hzn2u947iqh9ph2 true 203.2MiB mount /dest from exec copy /src-0 /dest/go/src/github.com/jessfraz/img ... sha256:9f131fba0383a6aaf25ecd78bd5f37003e41a4385d7f38c3b0cde352ad7676da true 958.6KiB pulled from docker.io/library/golang:alpine@sha256:a0045fbb52a7ef318937e84cf7ad3301b4d2ba6cecc2d01804f428a1e39d1dfc sha256:c4151b5a5de5b7e272b2b6a3a4518c980d6e7f580f39c85370330a1bff5821f1 true 472.3KiB pulled from docker.io/tonistiigi/copy@sha256:476e0a67a1e4650c6adaf213269a2913deb7c52cbc77f954026f769d51e1a14e sha256:ae4ecac23119cc920f9e44847334815d32bdf82f6678069d8a8be103c1ee2891 true 148.9MiB pulled from docker.io/library/debian:buster@sha256:a7789365b226786a0cb9e0f142c515f9f2ede7164a6f6be4a1dc4bfe19d5ec9c bkrjrzv3nvp7lvzd5cw9vzut7* true 4.879KiB local source for dockerfile sha256:db193011cbfc238d622d65c4099750758df83d74571e8d7498392b17df381207 true 467.2MiB pulled from docker.io/library/golang:alpine@sha256:a0045fbb52a7ef318937e84cf7ad3301b4d2ba6cecc2d01804f428a1e39d1dfc wn4m5i5swdcjvt1ud5bvtr75h* true 4.204KiB local source for dockerfile Reclaimable: 1.08GiB Total: 1.08GiB
Login to a Registry
$ img login -h Usage: img login [OPTIONS] [SERVER] Log in to a Docker registry. If no server is specified, the default (https://index.docker.io/v1/) is used. Flags: -backend backend for snapshots ([fuse naive overlayfs]) (default: naive) -d enable debug logging (default: false) -p Password (default: <none>) -password-stdin Take the password from stdin (default: false) -state directory to hold the global state (default: /tmp/img) -u Username (default: <none>)
Contributing
Please do! This is a new project and can use some love <3. Check out the issues.
The local directories are mostly re-implementations of buildkit interfaces to be unprivileged.
Acknowledgements
A lot of this is based on the work of moby/buildkit. Thanks @tonistiigi and @AkihiroSuda!