how to solve "ruby installation is missing psych" error?

I was having this error and noticed I had different versions of Ruby installed with HomeBrew, along with many gems that I no longer used. So did a full clean up like this:

$ brew remove --force ruby # remove all versions installed
$ sudo rm -rf /usr/local/lib/ruby # remove all gems and leftover files
$ brew install ruby
$ gem install bundler
$ bundle install

If you don't use a `Gemfile`, make sure you know which gems to reinstall.

In my case

rvm pkg install libyaml

and

rvm reinstall ruby-1.9.3-p125

solved the problem.


For people using Ubuntu, make sure that `libtool` is installed prior to the steps above:

sudo apt-get install libtool

For macOS users (with homebrew):

rm -rf /usr/local/lib/ruby/gems/ && brew reinstall ruby

In my case [all I needed to do][1] was

rm -rf /usr/local/lib/ruby/gems/2.4.0/gems/psych-2.2.4
rm -rf /usr/local/lib/ruby/gems/2.4.0/extensions/x86_64-darwin-16/2.4.0/psych-2.2.4

Now, FWIW, `gem list` includes

psych (2.2.4, default: 2.2.2)

[1]:

[To see links please register here]

- Ubuntu
- Using RVM
- Reason: Conflicting Psych gem versions between ruby 2.4.4 and ruby 2.5.1

I spent a few hours trying to get my error to go away and none of the replies here suited my case, so I thought I would post how I solved it...

In my case when I ran `gem list | grep psych`, I had the following output: `psych(default: 3.1.0, default: 3.0.2)`.

Apparently since version 2.5.0, ruby depends on the newer version of psych (3.1.0) and having both set as default was messing up everything. Notice that I never ended up finding out why those were both set as default - I completely wiped out rvm and ruby versions from my computer due to this.

So in order to remove the older version (3.0.2) from being set as default, head to `~/.rvm/gems/ruby-x.x.x@global/specifications/default`. If you run `ls | grep psych` it will return both versions of the gem here. If you want to maintain 3.1.0 as default just run `mv psych-3.0.2.gemspec ../` and then try running `gemlist` to make sure it is listing only one version as default now...

tl;dr
`cd /.rvm/gems/ruby-x.x.x@global/specifications/default`
`mv psych-3.0.2 ../`

Hope this helps someone!

I've been facing the same issue. I'm using MacPorts with `rbenv` installed!

What I did:
1. `sudo port install ruby26`
2. `sudo port select --set ruby ruby26` (this effectively takes macOS default ruby installation out of game)
3. removed all gems from `~/.gem/ruby/2.6.0/gems` which caused errors while invoking the `gem` command
4. run `gem pristine` commands for all gems listed by gem list (the exact commands are part of the warnings)
5. finally `gem update --user-install`

For problems with `rbenv` on `ubuntu 22`, I had to installl `libtool` and `libffi-dev` through apt, and compile the yaml package (Thanks to Dmitry for his answer):

sudo apt install libtool
sudo apt install libffi-dev

wget

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tar zxf yaml-0.2.5.tar.gz
cd yaml-0.2.5
./configure
make
make install


After that, I ran `rbenv install 3.2.2` again and it worked.