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76 lines
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76 lines
4.4 KiB
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https://github.com/checkpoint-restore/criu/actions/workflows/x86-64-gcc-test.yml)
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[](
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https://github.com/checkpoint-restore/criu/actions/workflows/docker-test.yml)
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[](
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https://github.com/checkpoint-restore/criu/actions/workflows/podman-test.yml)
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[](
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https://circleci.com/gh/checkpoint-restore/criu)
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<p align="center"><img src="https://criu.org/w/images/1/1c/CRIU.svg" width="256px"/></p>
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## CRIU -- A project to implement checkpoint/restore functionality for Linux
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CRIU (stands for Checkpoint and Restore in Userspace) is a utility to checkpoint/restore Linux tasks.
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Using this tool, you can freeze a running application (or part of it) and checkpoint
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it to a hard drive as a collection of files. You can then use the files to restore and run the
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application from the point it was frozen at. The distinctive feature of the CRIU
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project is that it is mainly implemented in user space. There are some more projects
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doing C/R for Linux, and so far CRIU [appears to be](https://criu.org/Comparison_to_other_CR_projects)
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the most feature-rich and up-to-date with the kernel.
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CRIU project is (almost) the never-ending story, because we have to always keep up with the
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Linux kernel supporting checkpoint and restore for all the features it provides. Thus we're
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looking for contributors of all kinds -- feedback, bug reports, testing, coding, writing, etc.
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Please refer to [CONTRIBUTING.md](CONTRIBUTING.md) if you would like to get involved.
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The project [started](https://criu.org/History) as the way to do live migration for OpenVZ
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Linux containers, but later grew to more sophisticated and flexible tool. It is currently
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used by (integrated into) OpenVZ, LXC/LXD, Docker, and other software, project gets tremendous
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help from the community, and its packages are included into many Linux distributions.
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The project home is at http://criu.org. This wiki contains all the knowledge base for CRIU we have.
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Pages worth starting with are:
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- [Installation instructions](http://criu.org/Installation)
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- [A simple example of usage](http://criu.org/Simple_loop)
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- [Examples of more advanced usage](https://criu.org/Category:HOWTO)
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- Troubleshooting can be hard, some help can be found [here](https://criu.org/When_C/R_fails), [here](https://criu.org/What_cannot_be_checkpointed) and [here](https://criu.org/index.php?title=FAQ)
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### Checkpoint and restore of simple loop process
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<p align="center"><a href="https://asciinema.org/a/232445"><img src="https://asciinema.org/a/232445.png" width="572px" height="412px"/></a></p>
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## Advanced features
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As main usage for CRIU is live migration, there's a library for it called P.Haul. Also the
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project exposes two cool core features as standalone libraries. These are libcompel for parasite code
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injection and libsoccr for TCP connections checkpoint-restore.
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### Live migration
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True [live migration](https://criu.org/Live_migration) using CRIU is possible, but doing
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all the steps by hands might be complicated. The [phaul sub-project](https://criu.org/P.Haul)
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provides a Go library that encapsulates most of the complexity. This library and the Go bindings
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for CRIU are stored in the [go-criu](https://github.com/checkpoint-restore/go-criu) repository.
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### Parasite code injection
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In order to get state of the running process CRIU needs to make this process execute
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some code, that would fetch the required information. To make this happen without
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killing the application itself, CRIU uses the [parasite code injection](https://criu.org/Parasite_code)
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technique, which is also available as a standalone library called [libcompel](https://criu.org/Compel).
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### TCP sockets checkpoint-restore
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One of the CRIU features is the ability to save and restore state of a TCP socket
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without breaking the connection. This functionality is considered to be useful by
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itself, and we have it available as the [libsoccr library](https://criu.org/Libsoccr).
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## Licence
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The project is licensed under GPLv2 (though files sitting in the lib/ directory are LGPLv2.1).
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All files in the images/ directory are licensed under the Expat license (so-called MIT).
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See the images/LICENSE file.
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