gem install rails - can't install

Hi, I have a rhel7 system and am trying to install the rails gem, I was
wondering how to troubleshoot this since I don't see any useful error
message. I'm guessing i'm just missing something, how to see what it
might be?

# gem install rails
Building native extensions. This could take a while...
ERROR: Error installing rails:
  ERROR: Failed to build gem native extension.

    /usr/bin/ruby extconf.rb
checking if the C compiler accepts ... yes
Building nokogiri using packaged libraries.
Using mini_portile version 2.0.0
checking for gzdopen() in -lz... yes
checking for iconv... yes

I think you are missing something that is required to build nokigiri.
I generally recommend using rvm to install ruby and rails, as rvm will
install all the requirements for you and will help you to manage
different versions of ruby and rails, but I don't know about using rvm
with rhel7. On ubuntu this would be as simple as

gpg --keyserver hkp://keys.gnupg.net --recv-keys
409B6B1796C275462A1703113804BB82D39DC0E3
\curl -L https://get.rvm.io | bash -s stable --rails

See rvm.io

Colin

My hypothesis would be missing headers and libraries for libxml2, libxslt
or ruby. What's inside mkmf.log?

# rpm -qa |grep libxml2
libxml2-python-2.9.1-6.el7_2.2.x86_64
libxml2-devel-2.9.1-6.el7_2.2.x86_64
libxml2-2.9.1-6.el7_2.2.x86_64

# rpm -qa |grep libxslt
libxslt-1.1.28-5.el7.x86_64
libxslt-devel-1.1.28-5.el7.x86_64

# cat /usr/local/share/gems/gems/nokogiri-1.6.7.2/ext/nokogiri/mkmf.log

"gcc -o conftest -I/usr/include -I/usr/include/ruby/backward
-I/usr/include -I. -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2
-fexceptions -fstack-protector-strong --param=ssp-buffer-size=4
-grecord-gcc-switches -mtune=generic -fPIC conftest.c -L. -L/usr/lib64
-L. -Wl,-z,relro -fstack-protector -rdynamic -Wl,-export-dynamic -m64
-lruby -lpthread -lrt -ldl -lcrypt -lm -lc "
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: int main(int argc, char **argv)
4: {
5: return 0;
6: }
/* end */

"gcc -I/usr/include -I/usr/include/ruby/backward -I/usr/include -I.
-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
-fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches
-mtune=generic -fPIC -m64 -Werror -c conftest.c"
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: int main() {return 0;}
/* end */

have_library: checking for gzdopen() in -lz... -------------------- yes

"gcc -o conftest -I/usr/include -I/usr/include/ruby/backward
-I/usr/include -I. -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2
-fexceptions -fstack-protector-strong --param=ssp-buffer-size=4
-grecord-gcc-switches -mtune=generic -fPIC -g -DXP_UNIX -Wall
-Wcast-qual -Wwrite-strings -Wconversion -Wmissing-noreturn -Winline
conftest.c -L. -L/usr/lib64 -L. -Wl,-z,relro -fstack-protector
-rdynamic -Wl,-export-dynamic -m64 -lruby -lz -lpthread -lrt -ldl
-lcrypt -lm -lc "
conftest.c: In function 't':
conftest.c:7:32: warning: variable 'p' set but not used
[-Wunused-but-set-variable]
int t(void) { void ((*volatile p)()); p = (void ((*)()))gzdopen; return
0; }
                                ^
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: #include <zlib.h>
4:
5: /*top*/
6: extern int t(void);
7: int t(void) { void ((*volatile p)()); p = (void ((*)()))gzdopen;
return 0; }
8: int main(int argc, char **argv)
9: {
10: if (argc > 1000000) {
11: printf("%p", &t);
12: }
13:
14: return 0;
15: }
/* end */

Did you run: sudo yum install -y rubygem-nokogiri before 'gem install nokogiri` ?

And sudo yum install -y gcc ruby-devel zlib-devel is recommended if you have problems.

source: http://www.nokogiri.org/tutorials/installing_nokogiri.html

Thanks for everyone's help,

Since the problem seemed to be with nokogiri, I managed to get it to
work with gem install nokogiri -- --use-system-libraries
However since there is a RPM for it, I should try that too.