uchuugaka / kerl

Easy building and installing of Erlang/OTP instances

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Easy building and installing of Erlang/OTP instances.

Kerl aims to be shell agnostic and its only dependencies, excluding what's required to actually build Erlang/OTP, are curl and git.

All is done so that, once a specific release has been built, creating a new installation is as fast as possible.

OTP Support Policy

As of 2017 November 8, we are supporting OTP builds back to R15. Older builds may or may not work. We will advance release support as new releases of OTP become available. For example, when OTP 21 is released, we will support Erlang builds R16 and newer.

Triage cadence

We triage kerl pull requests and issues at least once a month, typically on the fourth Tuesday of the month at 1 pm US/Pacific or 8 pm UTC.

IRC channel

We have a channel on freenode called #kerl - feel free to join and ask support or implementation questions any time. If no one is around, feel free to open an issue with your question or problem instead.


If you are on MacOS, and using homebrew, you can install kerl, along with shell completion, by running:

$ brew install kerl

Alternatively, you can download the script directly from github:

$ curl -O https://raw.githubusercontent.com/kerl/kerl/master/kerl

Then ensure it is executable

$ chmod a+x kerl

and drop it in your $PATH

Optionally download and install kerl's bash_completion file from https://github.com/kerl/kerl/raw/master/bash_completion/kerl

Optionally download and install kerl's zsh-completion file from https://github.com/kerl/kerl/raw/master/zsh_completion/_kerl

How it works

Kerl keeps tracks of the releases it downloads, builds and installs, allowing easy installations to new destinations (without complete rebuilding) and easy switches between Erlang/OTP installations.

By default, kerl downloads source tarballs from the official Erlang website, but you can tell kerl to download tarballs of Erlang source code from the tags pushed to the official source code by setting KERL_BUILD_BACKEND=git

You can also install directly from a raw git repository by using the kerl build git <git_url> <git_version> <build_name> syntax.


List the available releases (kerl ignores releases < 10):

$ kerl list releases
R10B-0 R10B-10 R10B-1a R10B-2 R10B-3 R10B-4 R10B-5 R10B-6 R10B-7 R10B-8 R10B-9 R11B-0 R11B-1 R11B-2 R11B-3 R11B-4 R11B-5 R12B-0 R12B-1 R12B-2 R12B-3 R12B-4 R12B-5 R13A R13B01 R13B02-1 R13B02 R13B03 R13B04 R13B R14A R14B01 R14B02 R14B03 R14B04 R14B R14B_erts- R15B01 R15B02 R15B02_with_MSVCR100_installer_fix R15B03-1 R15B03 R15B R16A_RELEASE_CANDIDATE R16B01 R16B02 R16B03-1 R16B03 R16B 17.0-rc1 17.0-rc2 17.0 17.1 17.3 17.4 17.5 18.0 18.1 18.2 18.2.1 18.3 19.0 19.1 19.2
Run '/usr/local/bin/kerl update releases' to update this list from erlang.org

Pick your choice and build it:

$ kerl build 19.2 19.2
Verifying archive checksum...
Checksum verified (7cdd18a826dd7bda0ca46d1c3b2efca6)
Extracting source code
Building Erlang/OTP 19.2 (19.2), please wait...
Erlang/OTP 19.2 (19.2) has been successfully built

Note that named builds allow you to have different builds for the same Erlang/OTP release with different configure options:

$ KERL_BUILD_DOCS=yes kerl build 19.2 19.2-builtdocs
Verifying archive checksum...
Checksum verified (7cdd18a826dd7bda0ca46d1c3b2efca6)
Extracting source code
Building Erlang/OTP 19.2 (19.2-builtdocs), please wait...
Building docs...
Erlang/OTP 19.2 (19.2-builtdocs) has been successfully built

(Note that kerl uses the otp_build script internally, and ./otp_build configure disables HiPE on linux)

You can verify your build has been registered:

$ kerl list builds

Now install a build to some location:

$ kerl install 19.2 ~/kerl/19.2
Installing Erlang/OTP 19.2 (19.2) in /Users/sanmiguel/kerl/19.2...
You can activate this installation running the following command:
. /Users/sanmiguel/kerl/19.2/activate
Later on, you can leave the installation typing:

Here again you can check the installation's been registered:

$ kerl list installations
19.2 /Users/sanmiguel/kerl/19.2

And at last activate it:

$ . /path/to/install/dir/activate

Activation will backup your $PATH, prepend it with the installation's bin/ directory. Thus it's only valid for the current shell session, and until you activate another installation or call kerl_deactivate.

You're now ready to work with your 19.2 installation:

$ erl -version
Erlang (SMP,ASYNC_THREADS,HIPE) (BEAM) emulator version 8.2

When you're done just call the shell function:

$ kerl_deactivate

Anytime you can check which installation, if any, is currently active with:

$ kerl active
The current active installation is:

You can get an overview of the current kerl state with:

$ kerl status
Available builds:
Available installations:
19.2 /Users/sanmiguel/kerl/19.2
The current active installation is:
There's no Dialyzer PLT for the active installation

You can delete builds and installations with the following commands:

$ kerl delete build 19.2
The 19.2 build has been deleted
$ kerl delete installation /path/to/install/dir
The installation in /path/to/install/dir has been deleted

You can easily deploy an installation to another host having ssh and rsync access with the following command:

$ kerl deploy anotherhost /path/to/install/dir
Cloning Erlang/OTP 19.2 (/path/to/install/dir) to anotherhost (/path/to/install/dir) ...
On anotherhost, you can activate this installation running the following command:
. /path/to/install/dir/activate
Later on, you can leave the installation typing:

Building from a github fork

It is possible to build Erlang from a github fork, by using the KERL_BUILD_BACKEND=git and setting OTP_GITHUB_URL to the URL of the fork. For example, to build Basho's OTP fork:

$ export OTP_GITHUB_URL="https://github.com/basho/otp"
$ kerl update releases
The available releases are:
R13B03 R13B04 R14A R14B R14B01 R14B02 R14B03 R14B04 R15A R15B R15B01 R15B01_basho1 R15B01p R15B02 R15B03 R15B03-1 R16A_RELEASE_CANDIDATE R16B R16B01 R16B01_RC1 R16B02 R16B02_basho R16B02_basho10 R16B02_basho10rc1 R16B02_basho10rc2 R16B02_basho10rc3 R16B02_basho2 R16B02_basho3 R16B02_basho4 R16B02_basho5 R16B02_basho6 R16B02_basho7 R16B02_basho8 R16B02_basho9 R16B02_basho9rc1 R16B03 R16B03-1 R16B03_yielding_binary_to_term 17.0 17.0-rc1 17.0-rc2 17.0.1 17.0.2 17.1 17.1.1 17.1.2 17.2 17.2.1 17.2.2 17.3 17.3.1 17.3.2 17.3.3 17.3.4 17.4 17.4.1 17.5 17.5.1 17.5.2 17.5.3 17.5.4 17.5.5 17.5.6 18.0 18.0-rc1 18.0-rc2 18.0.1 18.0.2 18.0.3 18.1 18.1.1 18.1.2 18.1.3 18.1.4 18.1.5 18.2 18.2.1 18.2.2 18.2.3 18.2.4 18.3 18.3.1 18.3.2 18.3.3 18.3.4 19.0 19.0-rc1 19.0-rc2 19.0.2

From here (provided the KERL_BUILD_BACKEND and OTP_GITHUB_URL variables remain in place), it is possible to use kerl as normal:

$ kerl build R16B02_basho10 16b02-basho10

Building from a git source

You can build Erlang directly from a git repository with a command of the form kerl build git <git_url> <git_version> <build_name> where <git_version> can be either a branch, a tag or a commit id that will be passed to git checkout:

$ kerl build git https://github.com/erlang/otp.git dev 19.2_dev
Checking Erlang/OTP git repository from https://github.com/erlang/otp.git...
Building Erlang/OTP 19.2_dev from git, please wait...
Erlang/OTP 19.2_dev from git has been successfully built


You can tune kerl using the .kerlrc file in your $HOME directory.

Locations on disk


Default: "$HOME"/.kerl Directory in which kerl will cache artefacts for building and installing.


Default: "$HOME"/.kerlrc File from which to source kerl configuration


Default: ${KERL_BASE_DIR}/archives Directory in which to place downloaded artefacts


Default: `${KERL_BASE_DIR}/builds Directory in which kerl will perform builds


Default: ${KERL_BASE_DIR}/gits Directory in which kerl will clone git repositories for building.

Build configuration


Space-separated options to pass to configure when building OTP.


Space-separated list of OTP applications which should exclusively be built.


Space-separated list of OTP applications to disable during building.


Create a PLT file alongside the built release.


Use autoconf during build process. NB: Automatically enabled when using KERL_BUILD_BACKEND=git


Default value: tarball Acceptable values: tarball, git

  • tarball: Fetch erlang releases from erlang.org
  • git: Fetch erlang releases from $OTP_GITHUB_URL

NB: Docs are only fetched when this is set to tarball. To enable creation of docs when set to git, one must also set $KERL_BUILD_DOCS.

NB: This setting has no effect when using kerl build git..., which invokes kerl to directly clone a git repository and build from there.


Default value: https://github.com/erlang/otp Acceptable value: any github fork of OTP, e.g. https://github.com/basho/otp


If $KERL_BUILD_DOCS is set, kerl will create docs from the built erlang version regardless of origin (tarball backend from erlang.org or via kerl build git, or via git backend).

If $KERL_BUILD_DOCS is unset, kerl will only install docs when NOT installing a build created via kerl build git..., and according to KERL_INSTALL_HTMLDOCS and KERL_INSTALL_MANPAGES.


Install man pages when not building from git source.

It's noteworthy that when not using KERL_BUILD_DOCS=yes, the docset that may be downloaded can be up to 120MB.


Install HTML documentation when not building from git source.

It's noteworthy that when not using KERL_BUILD_DOCS=yes, the docset that may be downloaded can be up to 120MB.


Build OTP to use SASL startup instead of minimal (default, when var is unset).

Installation configuration

Activation configuration

The following apply when activating an installation (i.e. . ${KERL_DEFAULT_INSTALL_DIR}/19.2/activate).


When set, automatically prefix the shell prompt with a section containing the erlang version (see $KERL_PROMPT_FORMAT ).


Default: (%BUILDNAME%) Available variables:

  • %BUILDNAME%: Name of the kerl build (e.g. my_test_build_18.0)
  • %RELEASE%: Name of the erlang release (e.g. 19.2 or R16B02)

The format of the prompt section to add.


Effective when calling kerl install <build> with no installation location argument.

If unset, $PWD is used.

If set, install the build under $KERL_DEFAULT_INSTALL_DIR/${buildname}.



Options passed to ssh and rsync during kerl deploy tasks.

Note on .kerlrc

Since .kerlrc is a dot file for /bin/sh, running shell commands inside the .kerlrc will affect the shell and environment variables for the commands being executed later. For example, the shell export commands in .kerlrc will affect your login shell environment when activating curl. Use with care.

Fish shell support

kerl has basic support for the fish shell.

To activate an installation:

source /path/to/install/dir/activate.fish

Deactivation is the same as in other shells:


Please note: if you've installed a build with an older version of kerl (1.2.0 older) it won't have the activate.fish script.

C shell support

kerl has basic support for the C shells (csh/tcsh/etc.).

To activate an installation:

source /path/to/install/dir/activate.csh

The activation script sources file .kerlrc.csh instead of .kerlrc.

Deactivation is the same as in other shells:


Please note: if you've installed a build with an older version of kerl it won't have the activate.csh script.


Here are the abstractions kerl is handling:

  • releases: Erlang/OTP releases from erlang.org

  • builds: the result of configuring and compiling releases or git repositories

  • installations: the result of deploying builds to filesystem locations (also referred to as "sandboxes")

Commands reference


kerl build <release_code> <build_name>
kerl build git <git_url> <git_version> <build_name>

Creates a named build either from an official Erlang/OTP release or from a git repository.

$ kerl build 19.2 19.2
$ kerl build git https://github.com/erlang/otp dev 19.2_dev


Configure options

You can specify the configure options to use when building Erlang/OTP with the KERL_CONFIGURE_OPTIONS variable, either in your $HOME/.kerlrc file or prepending it to the command line. Full list of all options can be in Erlang documentation.

$ KERL_CONFIGURE_OPTIONS=--enable-hipe kerl build 19.2 19.2-hipe
Configure applications

If non-empty, you can specify the subset of applications to use when building (and subsequent installing) Erlang/OTP with the KERL_CONFIGURE_APPLICATIONS variable, either in your $HOME/.kerlrc file or prepending it to the command line.

$ KERL_CONFIGURE_APPLICATIONS="kernel stdlib sasl" kerl build R15B01 r15b01_minimal
Configure disable applications

If non-empty, you can specify the subset of applications to disable when building (and subsequent installing) Erlang/OTP with the KERL_CONFIGURE_DISABLE_APPLICATIONS variable, either in your $HOME/.kerlrc file or prepending it to the command line.

$ KERL_CONFIGURE_DISABLE_APPLICATIONS="odbc" kerl build R16B02 r16b02_no_odbc
Enable autoconf

You can enable the use of autoconf in the build process setting KERL_USE_AUTOCONF=yes in your $HOME/.kerlrc file

Note: autoconf is always enabled for git builds

Using shell export command in .kerlrc

Configure variables which includes spaces such as those in CFLAGS cannot be passed on with KERL_CONFIGURE_OPTIONS. In such a case you can use shell export command to define the environment variables for ./configure. Note well: this method has a side effect to change your shell execution environment after activating a kerl installation of Erlang/OTP. Here is an example of .kerlrc for building Erlang/OTP for FreeBSD with clang compiler:

# for clang
export CC=clang CXX=clang CFLAGS="-g -O3 -fstack-protector" LDFLAGS="-fstack-protector"
# compilation options
KERL_CONFIGURE_OPTIONS="--disable-native-libs --enable-vm-probes --with-dynamic-trace=dtrace --with-ssl=/usr/local --with-javac --enable-hipe --enable-kernel-poll --with-wx-config=/usr/local/bin/wxgtk2u-2.8-config --without-odbc --enable-threads --enable-sctp --enable-smp-support"

In case you cannot access the default directory for temporary files (/tmp) or simply want them somewhere else, you can also provide your own directory with the variable TMP_DIR

export TMP_DIR=/your/custom/temporary/dir

Building documentation

Prior to kerl 1.0, kerl always downloaded prepared documentation from erlang.org. Now if KERL_BUILD_DOCS=yes is set, kerl will build the man pages and HTML documentation from the source repository in which is working.

Note: This variable takes precedent over the other documentation parameters.


kerl install <build_name> [path]

Installs a named build to the specified filesystem location.

$ kerl install 19.2 /srv/otp/19.2

If path is omitted the current working directory will be used. However, if KERL_DEFAULT_INSTALL_DIR is defined in ~/.kerlrc, KERL_DEFAULT_INSTALL_DIR/<build-name> will be used instead.

Install location restrictions

WARNING: kerl assumes the given installation directory is for its sole use. If you later delete it with the kerl delete command, the whole directory will be deleted, along with anything you may have added to it!

So please only install kerl in an empty (or non-existant) directory.

If you attempt to install kerl in $HOME or .erlang or $KERL_BASE_DIR, then kerl will give you an error and refuse to proceed. If you try to install kerl in a directory that exists and is not empty, kerl will give you an error.


SASL startup

You can have SASL started automatically setting KERL_SASL_STARTUP=yes in your $HOME/.kerlrc file or prepending it to the command line.

Manpages installation

You can have manpages installed automatically setting KERL_INSTALL_MANPAGES=yes in your $HOME/.kerlrc file or prepending it to the command line.

Note: for git-based builds, you want to set KERL_BUILD_DOCS=yes

HTML docs installation

You can have HTML docs installed automatically setting KERL_INSTALL_HTMLDOCS=yes in your $HOME/.kerlrc file or prepending it to the command line.

Note: for git-based builds, you want to set KERL_BUILD_DOCS=yes

Documentation installation

Man pages will be installed to [path]/man and HTML docs will be installed in [path]/html. The kerl activate script manipulates the MANPATH of the current shell such that man 3 gen_server or erl -man gen_server should work perfectly.

(Do not fret - kerl_deactivate restores your shell's MANPATH to whatever its original value was.)


kerl deploy <[user@]host> [directory] [remote_directory]

Deploys the specified installation to the given host and location.

$ kerl deploy anotherhost /path/to/install/dir

If remote_directory is omitted the specified directory will be used.

If directory and remote_directory is omitted the current working directory will be used.

NOTE: kerl assumes the specified host is accessible via ssh and rsync.


Additional SSH options

You can have additional options given to ssh by setting them in the KERL_DEPLOY_SSH_OPTIONS variable in your $HOME/.kerlrc file or on the command line, e.g. KERL_DEPLOY_SSH_OPTIONS='-qx -o PasswordAuthentication=no'.

Additional RSYNC options

You can have additional options given to rsync by setting them in the KERL_DEPLOY_RSYNC_OPTIONS variable in your $HOME/.kerlrc file or on the command line, e.g. KERL_DEPLOY_RSYNC_OPTIONS='--delete'.


kerl update releases

If KERL_BUILD_BACKEND=tarball this command fetches the up-to-date list of OTP releases from erlang.org.

If it is set to KERL_BUILD_BACKEND=git this command fetches an up-to-date list of OTP tags from the official OTP github repository.


kerl list <releases|builds|installations>

Lists the releases, builds or installations available.


kerl delete build <build_name>
kerl delete installation <path>

Deletes the specified build or installation.

$ kerl delete build 19.2
The 19.2 build has been deleted
$ kerl delete installation /srv/otp/19.2
The installation in /srv/otp/19.2 has been deleted


kerl active

Prints the path of the currently active installation, if any.

$ kerl active
The current active installation is:


kerl status

Prints the available builds and installations as well as the currently active installation.

$ kerl status
Available builds:
Available installations:
19.2 /srv/otp/19.2
19.2 /srv/otp/19.2_dev
No Erlang/OTP kerl installation is currently active


kerl path [installation]

Prints the path of the currently active installation if one is active. When given an installation name, it will return the path to that installation location on disk. This makes it useful for automation without having to run kerl's output through other tools to extract to path information.

$ kerl path
No active kerl-managed erlang installation

$ kerl path 19.2.3


kerl install-docsh

Important note: docsh only supports OTP versions 18 and later.

Install erl shell documentation access extension - docsh. This extends the shell with new helpers, which enable access to full function help (via h/{1,2,3}), function specs (s/{1,2,3}) and type information (t/{1,2,3}).

If you already have an OTP installation, you will need to remove it and re-install it before you execute install-docsh, since docsh needs some environment variables of its own to be set up and managed by the activate script.

Activating a docsh-enabled Erlang installation will try to create a $HOME/.erlang symlink. If this file exists (i.e. you have created it manually), please consider removing it - otherwise, docsh won't work. Deactivating the kerl Erlang installation will remove the symlink.

Alternatively, if the file exists and you have to keep it you can extend it with the content of a docsh-specific .erlang - this task is left as an exercise for the reader - and export KERL_DOCSH_DOT_ERLANG=exists to silence unwanted warnings. The manual setup guide will probably come in handy if you decide to take this route.

Compiling crypto on Macs

Apple stopped shipping OpenSSL in OS X 10.11 (El Capitan) in favor of Apple's own SSL library. That makes using homebrew the most convenient way to install openssl on macOS 10.11 or later. Additionally, homebrew stopped creating symlinks from the homebrew installation directory to /usr/local, so in response to this, if you're running El Capitan, Sierra, or High Sierra and you have homebrew installed, and you used it to install openssl, kerl will ask homebrew for the openssl installation prefix and configure Erlang to build with that location automatically.

Important: If you already have --with-ssl in your .kerlrc, kerl will honor that instead, and will not do any automatic configuration.

Compiling crypto on Red Hat systems

Red Hat believes there's a patent issue and has disabled elliptic curve crypto algorithms in its distributions for over 10 years.

This causes Erlang builds to die when its compiling its own crypto libraries.

As a workaround, you can set CFLAGS="-DOPENSSL_NO_EC=1" to tell the Erlang crypto libraries to not build the elliptic curve cipher suite.

This issue applies to Fedora, Red Hat Enterprise Linux, CentOS and all derivatives of those distributions.

There is a tracking issue to automatically set this compiler flag, if you wish to follow how kerl will eventually deal with this issue.


25 September 2018 - 1.8.5

  • Support Mojave builds (#301)
  • Disable SC2207 for Bash completion (#296)

3 August 2018 - 1.8.4

  • Support docsh 0.6.1 (#290)
  • Update docs about KERL_INSTALL_MANPAGES & HTML_DOCS (#292)
  • Fix bash completion for Bash 3 (#295)

3 July 2018 - 1.8.3

  • Update testing to include OTP 21 (#286)
  • Fix an issue affecting CD_PATH during builds (#284)

5 March 2018 - 1.8.2

  • Apply zlib patch when building OTP 17-19. (#258)
  • Add CircleCI (#246)
  • Fix empty package name warning (#245)

13 November 2017 - 1.8.1

  • Fix removing an installation by its name. (#244)

8 November 2017 - 1.8.0

  • Include support for installing and managing docsh (#213)
  • Fix a function name typo (#241)

23 October 2017 - 1.7.0

  • Suggest the proper activation script based on the shell you're using (#225)
  • Automatically turn on built-in shell history when using an OTP release >= 20 (#214)
  • Warn when a Linux does not appear to have a pre-requisite library/package to compile Erlang from source code. (#222)

2 October 2017 - 1.6.0

  • Support clang 9 and High Sierra command-line tools (CLT) on older Erlang builds. (#234)
  • Fix a pointer error in wx on macOS/clang 9 (#235)

25 May 2017 - 1.5.1

  • Bug Fix: Remove spurious spaces (#209)

24 May 2017 - 1.5.0

  • Published an OTP support policy, triage schedule, IRC channel
  • Apply build patches for Perls >= 5.22 on older OTP releases (#198)
  • Fix bad read usage (#200)
  • Add a force flag for mv (#201)
  • Use a more portable way to get perl minor release version (#204)
  • Force 64 bit flag on macOS (#205)
  • Fix documentation symlinks (#206)

22 February 2017 - 1.4.2

  • Fixed a syntax error when comparing hash outputs on reconfigurations (#191)
  • Added the path subcommand; enabled Travis-CI (#190)
  • Fixed mistakenly omitted version string from past 2 releases.

12 February 2017 - 1.4.1

  • Fix reading a checksum file for compile options (#180)
  • Get a little smarter about figuring out what apps to use when building a PLT file for dialyzer (#181)

5 February 2017 - 1.4.0

  • Fix environment variable handling and a typo (#179)
  • Overhaul the README; document all environment variables (#178)
  • Store build configuration in a file. Enables detecting if configuration has changed from build to build and also allows outputing build time options in kerl status (#177)
  • Assert perl exists before attempting build (#176); fixes issue #170

13 October 2016 - 1.3.4

  • Use a more portable way to restore PATH (#165)
  • Exit if curl fails. Download files if they are 0 length. (#166)

07 October 2016 - 1.3.3

  • Add support for (T)CSH (#155)
  • If homebrew is installed, make kerl check for a homebrew OpenSSL library path (#161)
  • If --enable-native-libs is active, make, clean and make again. (#163)

20 July 2016 - 1.3.2

  • Optionally enhance the activation prompt (#149)
  • Do not permit installation into a location that's already installed (#150)
  • Fix duplicate response from kerl prompt (fix #88) (#150)
  • Do not run if $HOME is not set. (fix #22) (#151)

16 July 2016 - 1.3.1

  • Fix argument order in archive unpacking (#146)
  • When building, show output of unmet dependencies or other build prerequisites (#148)

1 July 2016 - 1.3.0

  • basic fish shell support (#91)

28 June 2016 - 1.2.0

  • Make curl output more robust if using a .curlrc (#137)
  • Apply patches to build older Erlangs (#138)
  • Add a command to output a version string (#140)
  • Do not assume success for metadata file writes (#142)
  • Fix a grammar problem (#145)

20 May 2016 - 1.1.1

  • Remove valid directory check when doing a remote deployment.
  • Various get_otp_version() regex cleanup/fixes

14 May 2016 - 1.1.0

  • Remove support for Mac OS X Lion. Stop setting CFLAGS for better compiler optimizations. (#132)

14 May 2016 - 1.0.1

  • Be much more careful about installing into and removing directories. (#127)
  • Make OTP_GITHUB_URL and KERL_BUILD_BACKEND controllable from .kerlrc (#130)

2 May 2016 - 1.0

  • Support builds from git tags (#122)
  • Support documentation builds/installs from source code (#126)


Easy building and installing of Erlang/OTP instances


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