Container build and run tool
pip install plash==1.1588
[ http://plash.io/ ] [ https://travis-ci.org/ihucos/plash ] ████ ██ ████ ██ ██ ██ ██░███▒ ██ ▒████▓ ▒█████░ ██░████ ███████▒ ██ ██████▓ ████████ ███████▓ ███ ███ ██ █▒ ▒██ ██▒ ░▒█ ███ ▒██ ██░ ░██ ██ ▒█████ █████▓░ ██ ██ ██ ██ ██ ░███████ ░██████▒ ██ ██ ██░ ░██ ██ ██▓░ ██ ░▒▓██ ██ ██ ███ ███ ██▒ ██▒ ███ █▒░ ▒██ ██ ██ ███████▒ █████ ████████ ████████ ██ ██ ██░███▒ ░████ ▓███░██ ░▓████▓ ██ ██ ██ ██ ██ containerized Processes ### # What is plash? ### Plash is an implementation of containers, you can build and run containers. It uses the same underlying interfaces as other container software. ### # Some features ### - Unprivileged users are first-class citizens. - No daemons and no self baked privileged helpers. - It's portable and runs in many platforms like CI environments, itself or other container software. - Nested containers. - Create custom build commands with python3 - Designed for ergonomic command-line interface and scripting. - Integrates well with existing tools - "Do One Thing and Do It Well". ### # Getting started ### $ pip3 install plash $ plash --from alpine --apk xeyes -- xeyes $ plash --from-github ihucos/python --pip3 dotfiles -- dotfiles --sync $ plash --help ### # Documentation ### Reference documentation and tutorial: http://plash.io/ Examples: - https://github.com/ihucos/plash-travis-example Run plash in travis CI - https://github.com/ihucos/plash-python-example/ Example of OS-Level isolation of python packages - https://github.com/ihucos/plashmisc Custom build file commands (macros) - https://git.io/fAdM0 and https://git.io/fAdMg Run docker inside plash - https://github.com/ihucos/noapt Use Ubuntu packages in other Linux distributions - https://github.com/ihucos/megaman Use Arch Linux packages in other Linux distributions. - https://github.com/ihucos/plash-plash Example of running plash in plash ### # Backwards Compatibility ### One aim of plash is to have strong backwards compatibility. Breaking changes would have to be published under a different program name. It's unusual to launch a complex software with limited real world usage already claiming backward compatibility, this promise will not be fully kept in the beginning. As real bugs and design issues surface they will be fixed properly introducing breaking changes. Subtle things like exit status numbers may also change at this point. ### # Plashfiles ### Plashfiles are executable build files featuring an extendable, lightweight configuration management language. There may be many use cases like packaging scripts or bigger programs in a portable way. Here is an example: $ cat $HOME/bin/gtk-hello-world #!/usr/bin/env plash-exec --from archlinux --pacman gtk3 python-gobject --layer --entrypoint-script #!/usr/bin/env python import gi gi.require_version('Gtk', '3.0') from gi.repository import Gtk Gtk.init(None) Hello = Gtk.MessageDialog(message_type=Gtk.MessageType.INFO, buttons=Gtk.ButtonsType.OK, text="Hello world!", secondary_text="This is running inside a plash container.") Hello.run() ### # Some Recipes ### # export an image to docker $ plash export-tar --from alpine | docker import - # run an image from docker $ plash --from-docker busybox # run plash inside docker $ docker run --privileged --volume /var/lib/plash --volume /tmp -ti python bash root@5750a18ea217:/# pip3 install plash > /dev/null root@5750a18ea217:/# plash test 0_quickfail PASS basic-call-test PASS error-messages PASS macros/defpm PASS macros/eval-file PASS macros/eval-stdin PASS ... # run plash inside plash $ plash --from-github ihucos/python --apk unionfs-fuse --layer --pip3 plash localhost:/home/resu# plash test 0_quickfail PASS ... # use an image from https://images.linuxcontainers.org $ plash --from-lxc archlinux $ plash --from archlinux # actually --from fallbacks to --from-lxc # use an image from the web $ plash --from-url http://example.com/rootfs.tar # run a plash build file $ plash --eval-file ./mybuildfile # see how much space an image is taking $ plash with-mount --from alpine -- du -sh # delete an image $ plash rm --from ubuntu # Delete some older containers $ plash shrink # cleanup internal state (like tmp dirs) $ plash clean Check out the tutorial: http://plash.io/ ### # Conceptual differences ### Plash is actually conceptionally different to existing containers. Plash containers are more lightweight, in fact they are just processes. Let's take a look at this: Thread < Process < Container < Full Virtualisation < Dedicated Hardware ^ └─ plash is here Plash does not start containers, it starts processes. This architecture leverages the fact, that processes are a very well established interface. In order to list your containers, you use `ps` or `top`, to kill a "container" you can use `kill` and so on. To manage multiple instances, you can utilize something like `supervisord`, there is no need to reinvent and relearn things "the container way". Although containerized processes behave like - or in fact are - processes, they get the advantages of containers. Which is mainly the perception of running in a dedicated operating system of choice. Still some resources like the home folder and the network stack are shared. If a more heavy isolation is needed, other existing tools can provide this functionality, including for example other containerization platforms. ### # Requirements ### Note: in this sectiont the focus is on usability, not immaculate accuracy. For unprivileged use: - newuidmap/newgidmap - unionfs-fuse if not Ubuntu - Kernel >= 4.18 or Ubuntu - Support for user and mount namespaces For privileged use: - Support for mount namespaces Failsafe mode: - root access - chroot system call - a `mount` binary - Linux kernel or unionfs-fuse Warning: The failsafe mode does not clean up mountpoints. It is designed to run inside another short lived container/machine/mount namespace. Enable with `export PLASH_NO_UNSHARE=1` ### # Environment variables ### - PLASH_DATA Select a different directory for the build data. Default is "~/.plashdata" or "/var/lib/plash" if root. - PLASH_DEBUG If enabled, raises exceptions more often. - PLASH_EXPORT Tells plash which environment variables to export into containers. Separate multiple variables with a ":". - PLASH_INIT_UNION_TASTE Tells `plash init` which union filesystem to use for the build data. The default is "unionfs-fuse", the other alternative is "overlay". - PLASH_NO_UNSHARE The failsafe mode. It disables the attempt to create the mountpoints inside a fresh mount namespace. Setting this environment variable will pollute your current mount namespace. When run as a non-root user, this option has no effect. Only use this inside a throw-away mount namespace like another container. ### # Choosing an union filesystem ### By default after you run `plash init`, the build directory will be configured with the "unionfs-fuse" filesystem. If you want to use "overlay" instead, run the following command: `echo overlay | plash data tee config/union_taste` The difference is that "unionfs-fuse" is slower but more flexible, it works with fuse. Overlay on the other hand is faster but in most cases requires root access or an ubuntu system. If you can, go with "overlay". Note that "overlay" and "unionfs-fuse" may not be compatible to each other, so you have to decide for one of them right after initializing a build directory. It's like choosing the first Pokemon. ### # Development Guidelines ### - Keep the script character. - Don't fall in love with the code, embrace its absence. - All dependencies will get unmaintained at some point. - Use honest thin wrappers, documented leaky abstractions are better then difficult promises. - Don't be a monolith but don't try too hard not to be one. - Don't complain or warn via stderr, do it or don't do it. - Only be as smart as necessary and keep it simple and stupid (KISS). - Still be able to run this in five years without any maintenance work. - Find out what this program is and especially what it not is. - Say no to features, say yes to solved used cases. - Postpone compromises. - Be as vanilla as you can be - Be humble, don't oversell your abstraction layer. - Work toward a timeless, finished product that will require no maintainance. - Don't differentiate root from non-root users (this is a TODO) - The right guidelines for the right situation. ### # Caveats ### - Plash processes have the same operating system access rights than the process that started it. There is no security relevant isolation feature. Exactly as with running programs "normally", don't run programs you do not trust with plash and try to avoid using plash with the root user. - Sometimes there are issues with apt-get failing that still need to be ironed out, sometimes it's due to an older kernel, sometimes due the lxc ubuntu build and I suppose it could also be related to unionfs-fuse in certain cases. Currently I don't see a single solution for this, this problems will have to be managed and fixed bit by bit. Other package managers seem to be more robust. - Plash only runs inside Docker containers started with the `--privileged` flag, see GitHub issue #51 for details. ### # FAQ ### * Can I contribute? Please! Write me an mail mail@irae.me, open an issue, do a pull request or ask me out for a friendly chat about plash in Berlin. * Who are you? A Django/Python software-developer. Since this is an open source project I hope this software grows organically and collaboratively. * Why write a containerization software? Technical idealism. I wanted a better technical solution for a problem. In my personal opinion Docker is revolutionary but has some shortcomings: awkward interface, reinvention of established software or interfaces, bundling, vendor lock in and overengineering. In a way it kills it's idea by trying too hard to build a huge company on top of it. Plash thrives not to be more than a useful tool with one task: Building and running containerized processes. Ultimately I wanted something I can if necessary maintain by myself. * Are there plans to commercialise this? No, there isn't. At the same time I don't want to risk disappointing anyone and am not making any absolute guarantees. * What is the Licence? plash is licensed under the MIT Licence. * How does the code look? One python3 library without dependencies and one standalone script per subcommand. Counting the whole repository, it's just less than 5000 lines. The plan is to slowly rewrite part by part in C. But first I must learn C properly :-) * How does plash compare to Docker? There are no efforts to implement features like image distribution, process management, or orchestration in plash. Instead plash works nicely with docker or other software in the ecosystem. You can use plash to run docker in your system or run your plash containers inside docker. If you for exampling are using docker but want to have containers inside your docker container, you could use plash. You can also access docker images from plash or export plash images to docker. Another use case is to build docker images inside docker containers. They are two software with completely different philosophies. Docker is kind of a big framework that tries to solve all your container related problems. Plash on the other hand tries to be a flexible minimalistic command line tool that is only concerned with the essential needs of using containers. Both approaches are totally valid and very different. Comparing the code base between the two projects is also difficult. * Can I run this in production? You can. It probably still has some warts, what I can guarantee is to enthusiastically support this software and all issues that may come with it and focus on backward compatibility. * Is plash secure? Plash does not use any daemons or have its own setuid helper binaries. Note that plash does not try to isolate containers (which are just normal processes). That means that running a program inside plash is not a security feature. Running any container software introduces more entities to trust, that is the root file system image with its additional linux distribution and its own package manager. Using a program from alpine edge could be considered less secure than a package from debian stable or vice versa. Also note that keeping containers updated is more difficult than keeping "normal" system software updated. Furthermore note that programs could be not used to run inside semi-isolated containers and behave oddly. Plash uses unmodified lxc images and checks their signatures with gpgv (if in PATH). Using plash as root should be avoided and should not be necessary for most use cases. Until now plash was written by one person and of course I could be wrong about something. But generally speaking it really should be good enough.