Installing Erlang with kerl

At Electric Imp, on developer PCs, we manage our Erlang versions with kerl.

Assuming you have kerl available in your path (and you’ve installed the prerequisites), installing a version of Erlang is simple:

kerl update releases
kerl build 21.2 21.2
kerl install 21.2 $HOME/.kerl/erlangs/21.2

You can tweak the Erlang build by setting the KERL_CONFIGURE_OPTIONS environment variable. We don’t bother. If we did, we’d probably put a suffix on the build name and install directory.

The installation directory (~/.kerl/erlangs) was chosen to be similar to where kiex installs Elixir versions.

We prefer building from github, using a tag:

kerl build git https://github.com/erlang/otp.git OTP-21.2.4 OTP-21.2.4
kerl install OTP-21.2.4 $HOME/.kerl/erlangs/OTP-21.2.4

This gives us the option of installing a patched fork, which has been necessary in the past.

Note that you can set (e.g.) MAKEFLAGS=-j6 kerl build ... which will make the build quicker.

In this case, the build name and installation directory are named after the tag (OTP-21.2.4), which makes it easier to tell which versions were built from releases or from tags.

To activate the installation, you can do as kerl says:

. $HOME/.kerl/erlangs/OTP-21.2.4/activate

…or you can use direnv…

If you’re running short of disk space, you can delete old builds:

kerl cleanup all

This doesn’t delete the installed versions.