package irmin-unix

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Unix backends for Irmin


Dune Dependency






Irmin_unix defines Unix backends (including Git and HTTP) for Irmin, as well as a very simple CLI tool (called irmin) to manipulate and inspect Irmin stores.

Published: 07 Jun 2017


Irmin -- A distributed database that follows the same design principles as Git

Irmin is a library for persistent stores with built-in snapshot, branching and reverting mechanisms. It is designed to use a large variety of backends. Irmin is written in pure OCaml and does not depend on external C stubs; it aims to run everywhere, from Linux, to browsers and Xen unikernels.


Irmin is a library to version-control application data. It has the following features:

  • on-disk format various formats are supported, including the Git format: Irmin on-disk repositories can be inspected and modified using the classic Git command-line tools.

  • wire format various formats are supported, including the Git protocol (only in client mode) or a simple JSON-based REST API (client and server).

  • dynamic behaviour Irmin allows the users to define custom merge functions, to use in-memory transactions (to keep track of reads as well as writes) and to define event-driven workflows using a notification mechanism.

These abstractions allow developers to create applications with concurrent behaviors which are both efficient and safe.

Bindings to other languages


Irmin ships with various backends. It provides the following OCamlfind pacakges:

  • irmin.mem is an in-memory backend.

  • irmin.git uses the Git format to persist data on disk.

  • irmin.fs uses bin_prot to persist data on disk.

  • irmin.http uses JSON over HTTP to speak with an Irmin server.

Other external backends are available as external OPAM packages (use opam install <pkg> to install):

  • irmin-chunk stores raw contents into a well-balanced rope where leafs are chunks of all the same size.

  • irmin-indexdb is a backend for a web browser's IndexedDB store.


  • merge-queues is an implementation of mergeable queues.

  • merge-ropes is an implementation of mergeable ropes.

  • diff-datatypes is a collection of automatic merge functions based on edit scripts. It is fairly generic but contains specific implementation for mergeable trees, stacks and queues.

  • irmin-datatypes is a collection of mergeable datatypes, including LWW registers, queues and sets.


Here a list of Irmin users:

  • Cuekeeper a version-controlled TODO list in the browser.

  • imaplet, a version-controlled IMAP server and client.

  • jitsu, a DNS server that automatically starts unikernels on demand. The database is persisted with Irmin.

  • Irmin+Xenstore, the Xenstore deamon rewritten to use Irmin to persist its data.

  • irmin-arp, a distributed ARP cache.

  • dog, a synchronisation tool.

  • irminFS, a prototype version-controlled file-system using Fuse.

Further Reading

Getting Started


Irmin is packaged with opam:

opam install irmin-unix # install all the optional depencies

Irmin comes with a command-line tool called irmin. See irmin --help for further reading. Use either irmin <command> --help or irmin help <command> for more information on a specific command.

To get the full capabilites of Irmin, use the API:

open Lwt
open Irmin_unix
module Store =
  Irmin_git.FS (Irmin.Contents.String)(Irmin.Ref.String)(Irmin.Hash.SHA1)

let config = Irmin_git.config ~root:"/tmp/irmin/test" ~bare:true ()
let prog =
  Store.Repo.create config >>= Store.master task >>= fun t ->
  Store.update (t "Updating foo/bar")  ["foo"; "bar"] "hi!" >>= fun () ->
  Store.read_exn (t "Reading foo/bar") ["foo"; "bar"] >>= fun x ->
  Printf.printf "Read: %s\n%!" x;
let () = prog

To compile the example above, save it to a file called Install irmin and git with opam (opam install irmin-unix) and run

$ ocamlfind ocamlopt -o example -package irmin.unix,lwt.unix -linkpkg
$ ./example
Read: hi!

The examples directory contains more examples. To build them, run

$ ./configure --enable-examples
$ make

Tutorials are available on the wiki.


To report any issues please use the bugtracker on Github.


See the LICENSE file.


Development of Irmin was supported in part by the EU FP7 User-Centric Networking project, Grant No. 611001.

Dependencies (8)

  1. irmin-watcher >= "0.2.0"
  2. git-unix >= "1.11.0"
  3. irmin-fs >= "1.2.0" & < "2.0.0"
  4. irmin-http >= "1.2.0" & < "2.0.0"
  5. irmin-git >= "1.2.0" & < "2.0.0"
  6. irmin >= "1.2.0" & < "1.3.0"
  7. jbuilder >= "1.0+beta7"
  8. ocaml >= "4.01.0"

Dev Dependencies (3)

  1. mtime with-test & >= "1.0.0"
  2. alcotest with-test
  3. irmin-mirage with-test & >= "1.2.0" & < "2.0.0"

Used by (2)

  1. datakit-bridge-local-git >= "0.10.0"
  2. datakit-ci >= "0.10.0"




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