error gem file

When building native ruby gems, sometimes you'll get an error containing "ruby extconf.rb". This is often caused by missing dev libraries for the gem you're installing, or even ruby itself. Do you have apt installed on your machine? If not, I'd recommend installing it, it's a quick and easy way to get a lot of dev libraries. If you see people suggest installing "libmagick9-dev", that's an apt package that you'd install with:

$ sudo apt-get install libmagickwand-dev
or on centOs:

$ yum install ImageMagick-devel
On mac, you can use Homebrew:

$ brew install imagemagick

error mysql

error don't start mysqld:

==> delete /var/lib/mysql/ibdata1