用rvm安装ruby头文件
Travis CI使用RVM提供Ruby，但它似乎不包含标题：
$ find /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/zlib.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/dl.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/syck.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/socket.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/dbm.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/pty.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/strscan.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/io /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/io/console.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/io/wait.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/io/nonblock.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/iconv.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_14.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/gb2312.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_16.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/windows_1251.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/euc_jp.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_4.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_1.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/japanese_euc.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/emoji_sjis_softbank.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/single_byte.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/emoji_sjis_docomo.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/utf8_mac.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/gbk.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/emoji.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/japanese_sjis.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/big5.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/transdb.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/japanese.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/gb18030.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/utf_16_32.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/korean.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/escape.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/emoji_iso2022_kddi.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/chinese.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/iso2022.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/trans/emoji_sjis_kddi.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/encdb.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/utf_16le.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/gbk.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_8.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/euc_tw.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/koi8_r.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_9.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/utf_32le.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/big5.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/shift_jis.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/cp949.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/gb18030.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/koi8_u.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_7.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/utf_32be.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/euc_kr.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_15.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_10.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_3.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/utf_16be.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/emacs_mule.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_2.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_6.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_13.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_5.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/enc/iso_8859_11.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/json /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/json/ext /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/json/ext/generator.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/json/ext/parser.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/curses.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/fiber.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/racc /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/racc/cparse.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/stringio.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/bigdecimal.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/syslog.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/psych.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/rbconfig.rb /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/gdbm.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/date_core.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/pathname.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/etc.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/digest.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/dl /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/dl/callback.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/openssl.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/digest /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/digest/md5.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/digest/rmd160.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/digest/sha2.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/digest/sha1.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/digest/bubblebabble.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/sdbm.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/mathn /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/mathn/rational.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/mathn/complex.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/continuation.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/fcntl.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/objspace.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/readline.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/ripper.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/nkf.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/fiddle.so /home/vagrant/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/i686-linux/coverage.so 如何安装缺少的标题（ ruby.h和朋友）？
你在错误的位置检查，检查：
$ find /home/mpapis/.rvm/rubies/ruby-1.9.3-p194/ -name ruby.h /home/mpapis/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby/ruby.h /home/mpapis/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby.h
有一个选项可以传递给rvm install ，这将强制rvm从源代码编译ruby实例：
rvm install --disable-binary
这使我成功安装fog及其依赖nokogiri成为可能。
我在GitHub线程中遇到了这个解决方案; 它是由mpapis发布的。