mkmf.rb can't find header files for ruby at /usr/lib/ruby/ruby.h

/usr/bin/ruby extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/ruby.h
Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/ffi-1.9.6 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/ffi-1.9.6/ext/ffi_c/gem_make.out

If you are using CentOS, fedora or RHEL, Run command

sudo yum install ruby-devel

If you are using debian or ubuntu, Run command

sudo apt-get install ruby-dev

nodejs npm - Fatal error: unable to find local grunt

Fatal error: unable to find local grunt

You need to install grunt on your system.
All the explanations are here.

To solve this problem, Run following command in terminal :

npm install -g grunt-cli
npm install grunt --save-dev
npm install grunt-cli

cronjob is running at wrong timezone

cronjob time zone is wrong

First check hardware time and timezone using command

hwclock

If it is different than system time, it may be possible that your cron is following hardware time.

Set your hardware clock time same as system time using command

hwclock -w

Now check if cron is following correct time zone.

If you are still facing problem, Restart cron daemon once.
You need to restart cron when you change your time zone.

If you are still facing problem, Restart your system once.