How to install opam

This page describes how to install and configure opam and external solvers. For further help on how to use opam, either read opam --help or move on to the Usage guide.

Upgrading from a previous version

Generally, you should just reproduce the same installation steps as for the original installation: upgrade from your system's package manager, or re-run the binary installer. Opam will automatically update its internal repository at ~/.opam on first run if needed (backup that if you may want to rollback the upgrade without starting over).

Binary distribution

The quickest way to get the latest opam up and working is to run:

wget -O - | sh -s /usr/local/bin

This will simply check your architecture, download and install the proper pre-compiled binary and run opam init.

We provide pre-compiled binaries for:

  • Linux i686, amd64 and arm7
  • OSX (intel 64 bits) (other platforms are available using the other methods below)

You can pick your download here, and simply put it in your PATH as opam, e.g.

sudo cp <downloaded file> /usr/local/bin

Using your distribution's package system

This is generally the recommended way, when available and up-to-date. Here is a list of supported distributions:


The opam and opam-git packages are available in the AUR. Replace opam with opam-git in the following instruction to get the development version:

yaourt -S opam


Binary packages of opam are available for the stable (a bit outdated), testing and unstable distributions, from the official repositories. You should be set with:

apt-get install opam

There are also unofficial packages from the OpenSUSE Build Service, for the latest version, when not yet in the Debian repositories:

apt-key add - < Release.key
echo 'deb /' >> /etc/apt/sources.list.d/opam.list
apt-get update


The dev-ocaml/opam package can be installed with the command:

cave resolve -x dev-ocaml/opam

You might need to add the ::ocaml-unofficial repository first:

cave resolve -x repository/ocaml-unofficial

Fedora, CentOS and RHEL

RPMs for Fedora, CentOS and Red Hat Enterprise Linux are available with instructions on the OpenSUSE Build Server.


The opam package for Mageia can be installed with the command:

urpmi opam


Opam builds via sources fine on OpenBSD 5.6 or earlier, and is available in the ports and packages tree on OpenBSD 5.7 or higher.

cd /usr/ports/sysutils/opam
make install

Note that the aspcud external solver is not yet available on OpenBSD, so you may see some odd upgrade attempts due to the use of the internal solver.


Opam packages for homebrew and MacPorts are available:

brew install opam                   # Homebrew, OSX Mavericks or later
brew install opam --without-aspcud  # Homebrew, OSX Mountain Lion or lower
port install opam                   # MacPort

See also howto setup for Opam usage.


Warning: although there is an opam package available officially in "Utopic" (14.10), it's currently broken. Don't use it, see the bug report. The Ubuntu "Vivid" (15.04) package is fine.

We provide binary packages for "Precise" and "Trusty"

add-apt-repository ppa:avsm/ppa
apt-get update
apt-get install ocaml ocaml-native-compilers camlp4-extra opam

There are also PPAs available that are pinned to specific revisions of OCaml and opam -- we use them for our automated testing.

If the command add-apt-repository is not available, you can install the package software-properties-common with apt-get install software-properties-common. Alternatively, you may manually edit the file /etc/apt/sources.list to add the PPA for your Ubuntu release.

From Sources

Getting the Sources

Sources of the latest stable version of opam are available on Github:

You can also download the full archives, including opam dependencies (these don't require any extra downloads, just the OCaml compiler -- 3.12.1 or later):

  • 1.2.2 MD5: 7d348c2898795e9f325fb80eaaf5eae8 SHA1: 415ff0506378ab8dfa428fcd0aff3aa28337d93b
  • 1.2.1 MD5: 04e8823a099ab631943952e4c2ab18fc SHA1: 189e309ee0659723abaaad5f887f5caf89b34422
  • 1.2.0 MD5 (opam-full-1.2.0.tar.gz) = 17cc252c6c80fc503c4878eac8d123e7
  • 1.1.2 MD5 (opam-full-1.1.2.tar.gz) = ba2a4136b65003c04d905de786f3c3ab
  • 1.1.1 MD5 (opam-full-1.1.1.tar.gz) = a7bebe947b3e6c1c10ccafabb839d374
  • 1.1.0 MD5 (opam-full-1.1.0.tar.gz) = d6e2f56b10c0be73b5677963e6659d24

Follow the instructions in the included to get opam built and installed from there.

Using ocamlbrew

ocamlbrew is a script that can bootstrap an OCaml environment including opam, from source. This option does not require an existing OCaml installation, or a pre-compiled opam binary for your platform. To bootstrap a new OCaml environment including opam, make sure that you have the necessary pre-requisites installed to run ocamlbrew, and then run:

curl -kL | env OCAMLBREW_FLAGS="-r" bash

External Solvers

Resolving package installations in the presence of dependencies and conflicts is known to be an NP-complete problem. Thankfully, a big effort has already been put into solving it very efficiently: opam relies on this effort and delegates the solving process to external solvers. opam integrates a simple solver, so it can used without any extra dependencies, but for best results you should have one of those solvers on your system:

  • aspcud (recommended)
  • packup
  • mccs (no built-in support at the moment, but may be used with the following solver configuration string: mccs -i %{input}% -o %{output}% -lexagregate[%{criteria}%].)
  • p2Cudf, which may be the easiest if dependencies are a problem, as it comes as a single jar file. Dowload it and set the solver configuration string to java -jar <jarfile-location> -obj %{criteria}% %{input}% %{output}%.

We recommend installing one through your packaging system whenever possible: this should already have been taken care of if you installed opam through your packaging system. If you have trouble installing an external solver and have reliable network connectivity, Irill kindly provides a "Solver farm" which can be used as a remote solver by opam.

If you use the internal solver only, the following symptoms may be sign that you need an external solver: very bad upgrade proposals, or dependency solving becoming very slow.

Opam will detect the availability of aspcud or packup commands on your system and should switch to using them directly. You can explicitly specify which external solver to use by using the --solver command-line argument, the $OPAMEXTERNALSOLVER environment variable, or the solver: field in the ~/.opam/config file.

External solvers also allow to specify fine-grained preferences. aspcud is currently recommended because it supports a richer language of solver preferences giving opam more control over the requested solution.