Erlang disappeared from /usr/bin/erl

Question

The setting

I have downloaded rabbitMQ and used it on an EC2 14.04 machine for a few days.

The setting was simple - I downloaded the Binary .tar.gz, opened it, and typed:

sbin/rabbitmq-server

RabbitMQ started and everything worked fine.

When I opened the machine this morning and tried to start rabbitMQ the same way, I got:

ubuntu rabbitmq-server: erl: not found

First, I was looking for erl:

$ locate erl | grep "erl$" | grep -v perl
/usr/bin/erl
/usr/bin/run_erl
/usr/bin/to_erl
/usr/share/doc/erlang-xmerl

But:

$ ls /usr/bin/erl
ls: cannot access /usr/bin/erl: No such file or directory

This means that erlang was there a few hours ago, before the last update of locate, but was somehow deleted!

I have re-installed erlang using apt-get and everything works well.

Why was erlang deleted from my machine? How can I prevent this from happening in the future?

you could make the file immutable by using `chattr +i`, but then you'd need to make it mutable each time Erlang was to be updated. I don't remember if the root user can modify immutable files without first making them mutable or not. — Alexej Magura, Dec 31 '14 at 10:24