这篇文章不记录Gitlab的使用方法，更不说明Gitlab的特性，只记录的升级步骤以及遇到的问题。
由于升级的版本跨度有点大，Gitlab本身的备份\还原并不适合此次的迁移。

部署环境：

 阿里云ECS 4核\8G\40G  CentOS 7.3.1611
 阿里云RDS PostgreSQL 9.4
 gitlab-ce-9.3.4-ce.0.el7.x86_64
 nginx/1.10.2

迁移流程：
1、在新机器上部署GitLab，我们采用RPM包的方式安装。
2、编辑/etc/gitlab/gitlab.rb

external_url 'https://gitlab.xxxxx.com'  #git的URL，启用SSL就写https，反之就写http
gitlab_rails['time_zone'] = 'UTC'
gitlab_rails['gitlab_email_enabled'] = true  #启用Email
gitlab_rails['gitlab_email_from'] = 'user@host.com'
gitlab_rails['gitlab_email_display_name'] = 'Gitlab email notification'
gitlab_rails['db_adapter'] = "postgresql"      #gitlab使用的数据库，mysql/postgresql
gitlab_rails['db_encoding'] = "utf8"
gitlab_rails['db_collation'] = nil
gitlab_rails['db_database'] = "gitlab_production"
gitlab_rails['db_pool'] = 10
gitlab_rails['db_username'] = "gitlab_user"
gitlab_rails['db_password'] = "*********"
gitlab_rails['db_host'] = "xxxx.pg.aliyun.com"
gitlab_rails['db_port'] = 3433
gitlab_rails['db_socket'] = nil
gitlab_rails['db_sslmode'] = nil
gitlab_rails['db_sslrootcert'] = nil
gitlab_rails['db_prepared_statements'] = true
gitlab_rails['db_statements_limit'] = 1000
gitlab_rails['smtp_enable'] = true
gitlab_rails['smtp_address'] = "smtpdm.aliyun.com"
gitlab_rails['smtp_port'] = 25
gitlab_rails['smtp_user_name'] = "user@host.com"
gitlab_rails['smtp_password'] = "******"
gitlab_rails['smtp_domain'] = "user@host.com"
gitlab_rails['smtp_authentication'] = "login"
gitlab_rails['smtp_enable_starttls_auto'] = true
gitlab_rails['smtp_tls'] = false
postgresql['enable'] = false                                    #禁用自带postgressql
web_server['external_users'] = ['nginx']
nginx['enable'] = false                                            #禁用自带nginx
prometheus['enable'] = true
prometheus['monitor_kubernetes'] = true
prometheus['username'] = 'gitlab-prometheus'
prometheus['uid'] = nil
prometheus['gid'] = nil
prometheus['shell'] = '/bin/sh'
prometheus['home'] = '/var/opt/gitlab/prometheus'
prometheus['log_directory'] = '/var/log/gitlab/prometheus'
prometheus['scrape_interval'] = 15
prometheus['scrape_timeout'] = 15
prometheus['chunk_encoding_version'] = 2
prometheus['listen_address'] = '0.0.0.0:9090'                #修改prometheus的监听地址
prometheus_monitoring['enable'] = true

3、由于这台机器有好几个访问域名，需要共用一个nginx，所以就没用gitlab自带的Nginx。
配置nginx:

cat /etc/nginx/nginx.conf

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;

# Load dynamic modules. See /usr/share/nginx/README.dynamic.
include /usr/share/nginx/modules/*.conf;

events {
    worker_connections 1024;
}

http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"'
                      '$connection $upstream_addr '
                      'upstream_response_time $upstream_response_time';

    access_log  /var/log/nginx/access.log  main;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 2048;
        server_tokens off;

    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;
        client_body_buffer_size 3072k;
        proxy_buffers           16 2048k;
        proxy_buffer_size       512k;

        connection_pool_size            256;
        client_header_buffer_size       1k;
        large_client_header_buffers     8 4k;
        request_pool_size               4k;
        client_max_body_size            128m ;

        output_buffers  1 32k;
        postpone_output 1460;

        ignore_invalid_headers  on;

        gzip on;
        gzip_disable "msie6";
        gzip_proxied    expired no-cache no-store private auth;
        gzip_types text/plain application/json application/x-javascript text/css application/xml application/xml+rss text/javascript application/javascript application/soap+xml;
        gzip_http_version 1.1;
        #gzip_comp_level 6;
        # gitlab
        proxy_cache_path proxy_cache keys_zone=gitlab:10m max_size=1g levels=1:2;
        proxy_cache gitlab;
        map $http_upgrade $connection_upgrade {
            default upgrade;
            ''      close;
        }

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;
}

cat /etc/nginx/conf.d/gitlab-http.conf

upstream gitlab-workhorse {
  server unix:/var/opt/gitlab/gitlab-workhorse/socket;
}


server {
  listen *:443 ssl http2;


  server_name gitlab.xxxx.com;
  server_tokens off; ## Don't show the nginx version number, a security best practice

  ## Increase this if you want to upload large attachments
  ## Or if you want to accept large git objects over http
  client_max_body_size 0;

  ## Strong SSL Security
  ## https://raymii.org/s/tutorials/Strong_SSL_Security_On_nginx.html & https://cipherli.st/
  ssl on;
  ssl_certificate /etc/gitlab/ssl/gitlab.xxxx.com.pem;
  ssl_certificate_key /etc/gitlab/ssl/gitlab.xxxx.com.key;

  # GitLab needs backwards compatible ciphers to retain compatibility with Java IDEs
  ssl_ciphers 'ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4';
  ssl_protocols  TLSv1 TLSv1.1 TLSv1.2;
  ssl_prefer_server_ciphers on;
  ssl_session_cache  builtin:1000  shared:SSL:10m;
  ssl_session_timeout  5m;


  ## Real IP Module Config
  ## http://nginx.org/en/docs/http/ngx_http_realip_module.html

  ## HSTS Config
  ## https://www.nginx.com/blog/http-strict-transport-security-hsts-and-nginx/
  add_header Strict-Transport-Security "max-age=31536000";

  ## Individual nginx logs for this GitLab vhost
  access_log  /var/log/nginx/gitlab_access.log main;
  error_log   /var/log/nginx/gitlab_error.log;

  if ($http_host = "") {
    set $http_host_with_default "gitlab.xxxx.com";
  }

  if ($http_host != "") {
    set $http_host_with_default $http_host;
  }

  ## If you use HTTPS make sure you disable gzip compression
  ## to be safe against BREACH attack.
  gzip off;

  ## https://github.com/gitlabhq/gitlabhq/issues/694
  ## Some requests take more than 30 seconds.
  proxy_read_timeout      3600;
  proxy_connect_timeout   300;
  proxy_redirect          off;
  proxy_http_version 1.1;

  proxy_set_header Host $http_host_with_default;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_set_header Upgrade $http_upgrade;
  proxy_set_header Connection $connection_upgrade;
  proxy_set_header X-Forwarded-Proto https;
  proxy_set_header X-Forwarded-Ssl on;

  location ~ (\.git/gitlab-lfs/objects|\.git/info/lfs/objects/batch$) {
    proxy_cache off;
    proxy_pass http://gitlab-workhorse;
    proxy_request_buffering off;
  }

  location / {
    proxy_cache off;
    proxy_pass  http://gitlab-workhorse;
  }

  location /assets {
    proxy_cache gitlab;
    proxy_pass  http://gitlab-workhorse;
  }

  error_page 404 /404.html;
  error_page 422 /422.html;
  error_page 500 /500.html;
  error_page 502 /502.html;
  location ~ ^/(404|422|500|502)(-custom)?\.html$ {
    root /opt/gitlab/embedded/service/gitlab-rails/public;
    internal;
  }
}

cat /etc/nginx/conf.d/nginx-status.conf

server  {
    listen *:8060;
    server_name localhost;
    location /nginx_status {
      stub_status on;
      server_tokens off;
      access_log off;
      allow 127.0.0.1;
      deny all;
    }
}

4、备份原Gitlab的PostgreSQL的数据库：

 # /opt/gitlab/embedded/bin/pg_dump -h xxxx1.pg.rds.aliyuncs.com -p 3433 -U gitlab_user -W  gitlabhq_production > gitlabhq_production.sql
 # /opt/gitlab/embedded/bin/psql -h xxxx2.pg.rds.aliyuncs.com -p 3433 -U gitlab_user -W  gitlabhq_production < gitlabhq_production.sql

备份时可能会由于pg_dump的版本较低，会报错，可以尝试替换pg_dump的版本再去备份，（我是直接copy的pg_dump_9.6到当期主机进行的dump）。
5、备份原主机的 /var/opt/gitlab/目录下的git-data、gitlab-ci 、gitlab-rails/{uploads shared }并copy的新主机上进行目录替换。
6、将新机器的/etc/gitlab/gitlab-secrets.json替换成原来机器上的，不然会导致gitlab-ci的pipeline报“500 error”。
7、替换完成后就是一系列的检查、数据迁移、缓存清楚等工作

 # gitlab-rake gitlab:env:info  #检查环境和配置是否正确
 # gitlab-rake gitlab:check   #检查，检查结果会告诉你如何纠正错误。
 # gitlab-rake db:migrate   #迁移完db后需要执行此步骤。
 # gitlab-rake gitlab:shell:setup RAILS_ENV=production  #重新生成ssh key
 # gitlab-rake cache:clear  #清除缓存

大体的流程差不多就这些，下面附加一些可能用的操作命令：

登录gitlab自带的postgreqsl：
  #su - gitlab-psql  
  #gitlab-psql gitlabhq_production
 或
  #sudo -u gitlab-psql /opt/gitlab/embedded/bin/psql -h /var/opt/gitlab/postgresql -d gitlabhq_production

登录阿里云RDS-PostgreSQL：
  # /opt/gitlab/embedded/bin/psql -h xxxx2.pg.rds.aliyuncs.com -p 3433 -U gitlab_user -W  -d gitlabhq_production

登录redis：
   #/opt/gitlab/embedded/bin/redis-cli -s /var/opt/gitlab/redis/redis.socket "$@"