总结最近安装Redmine3.4.5的操作步骤：
1、安装必要的系统软件包：httpd,Passenger等

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yum install openssl-devel readline-devel zlib-devel curl-devel libyaml-devel libffi-devel
yum install mariadb-devel
yum install httpd httpd-devel
yum install ImageMagick ImageMagick-devel

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2、安装编译Ruby 2.5.1
    过程中无法执行gem sources --add https://ruby.taobao.org，解决方法：

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yum install libssl-dev libssl rvm
cd /usr/local/ruby-2.5.1/ext/openssl
ruby extconf.rb --with-openssl-include=/usr/include/openssl --with-openssl-lib=/usr/lib64/openssl/
ln -s /usr/local/ruby-2.5.1/include /
cd /usr/local/ruby-2.5.1/ext/zlib
ruby ./extconf.rb
make
make install
gem sources --add https://gems.ruby-china.org/

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3、安装bundle；设置MariaDB；
gem install bundler --no-rdoc --no-ri
vi /etc/my.cnf
   character-set-server=utf8

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4、安装Redmine3.4.5
cd /var/lib/redmine/
vi config/database.yml

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5、安装gem的依赖
bundle install --without development test --path vendor/bundle

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6、Redmine管理平台初始设置
bundle exec rake generate_secret_token  
*****（由于执行bundle exec rake generate_secret_token会报错显示request_store等需要gem install，尝试执行了bundle install，报错rbpdf-1.19.3.gem已被破坏，我找到rbpdf-1.19.3.gem所在的目录/var/lib/redmine/vendor/bundle/ruby/2.5.0/，删除之，再做bundle install，OK了）*****
     再继续执行；    
RAILS_ENV=production bundle exec rake db:migrate

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7、安装Passenger  （Centos默认已安装）
8、检查http设置，并重启httpd生效

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service httpd configtest
service httpd restart
    登陆Redmine网页服务。
Centos-7下安装Redmine-3.pdf