1.ERROR: While executing gem ... (Gem::Exception) Unable to require openssl, install OpenSSL and rebuild ruby (preferred) or use non-HTTPS sources

方法：

进入ruby源码解压包，进入ruby 源码包下的 ext/openssl ，用ruby自带的openssl编译，而不是yum 的openssl

cd/root/ruby-2.1.5/ext/opensslrubyextconf.rb成功...make报错....make:***Noruletomaketarget`/thread_native.h',neededby`ossl.o'.Stop.解决方法：打开MakefilevimMakefile加入第三行路径，也就是【top_srcdir=/root/ruby-2.1.5】srcdir=.topdir=/usr/local/ruby/include/ruby-2.1.0top_srcdir=/root/ruby-2.1.5hdrdir=$(topdir)保存退出，makeclean，重新make,成功，makeinstall成功[root@mysqlopenssl]#makelinkingshared-objectopenssl.so[root@mysqlopenssl]#makeinstall/usr/bin/install-c-m0755openssl.so/usr/local/ruby/lib/ruby/site_ruby/2.1.0/x86_64-linuxinstallingdefaultopenssllibraries



2.

gem install mysql2

Fetching:mysql2-0.4.3.gem(100%)Buildingnativeextensions.Thiscouldtakeawhile...ERROR:Errorinstallingmysql2:ERROR:Failedtobuildgemnativeextension./usr/local/ruby/bin/ruby-r./siteconf20160321-3049-192s9jh.rbextconf.rbcheckingforruby/thread.h...yescheckingforrb_thread_call_without_gvl()inruby/thread.h...yescheckingforrb_thread_blocking_region()...yescheckingforrb_wait_for_single_fd()...yescheckingforrb_hash_dup()...yescheckingforrb_intern3()...yescheckingformysql_query()in-lmysqlclient...no-----mysqlclientismissing.Youmayneedto'apt-getinstalllibmysqlclient-dev'or'yuminstallmysql-devel',andtryagain.-----***extconf.rbfailed***CouldnotcreateMakefileduetosomereason,probablylackofnecessarylibrariesand/orheaders.Checkthemkmf.logfileformoredetails.Youmayneedconfigurationoptions.Providedconfigurationoptions:--with-opt-dir--without-opt-dir--with-opt-include--without-opt-include=${opt-dir}/include--with-opt-lib--without-opt-lib=${opt-dir}/lib--with-make-prog--without-make-prog--srcdir=.--curdir--ruby=/usr/local/ruby/bin/ruby--with-mysql-dir--without-mysql-dir--with-mysql-include--without-mysql-include=${mysql-dir}/include--with-mysql-lib--without-mysql-lib=${mysql-dir}/lib--with-mysql-config--without-mysql-config--with-mysql-dir--without-mysql-dir--with-mysql-include--without-mysql-include=${mysql-dir}/include--with-mysql-lib--without-mysql-lib=${mysql-dir}/lib--with-mysqlclientlib--without-mysqlclientlib


已经讲的很清楚了，安装mysql-devel

yum install mysql-devel