Т.е. у вас в конфиге должно быть что-то типа:
launch=gmysql,gmysql:server2
gmysql-host=192.168.1.1
gmysql-user=...
gmysql-password=...
gmysql-dbname=...
gmysql-server2-host=192.168.2.2
gmysql-server2-user=...
gmysql-server2-password=...
gmysql-server2-dbname=...
вообще я никогда не настраивал и не админил PowerDNS (использую другое ПО), только название это встречал, все эти настройки в первый раз вижу. Но вот немного погуглил и мне к рабочиепонравилось, что есть много информации и всё так хорошо и подробно расписано.
** Invoke gitlab:backup:create (first_time)
** Invoke gitlab_environment (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute gitlab_environment
** Execute gitlab:backup:create
** Invoke gitlab:backup:db:create (first_time)
** Invoke gitlab_environment
** Execute gitlab:backup:db:create
Dumping database ...
rake aborted!
NameError: uninitialized constant Backup::Database
/opt/gitlab/embedded/service/gitlab-rails/lib/tasks/gitlab/backup.rake:99:in `block (4 levels) in '
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `block in execute'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `each'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `execute'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:213:in `block in invoke_with_call_chain'
/opt/gitlab/embedded/lib/ruby/2.5.0/monitor.rb:226:in `mon_synchronize'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:193:in `invoke_with_call_chain'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:182:in `invoke'
/opt/gitlab/embedded/service/gitlab-rails/lib/tasks/gitlab/backup.rake:10:in `block (3 levels) in '
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `block in execute'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `each'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `execute'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:213:in `block in invoke_with_call_chain'
/opt/gitlab/embedded/lib/ruby/2.5.0/monitor.rb:226:in `mon_synchronize'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:193:in `invoke_with_call_chain'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/task.rb:182:in `invoke'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:160:in `invoke_task'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:116:in `block (2 levels) in top_level'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:116:in `each'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:116:in `block in top_level'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:125:in `run_with_threads'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:110:in `top_level'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:83:in `block in run'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:186:in `standard_exception_handling'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/lib/rake/application.rb:80:in `run'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/rake-12.3.1/exe/rake:27:in `'
/opt/gitlab/embedded/bin/rake:23:in `load'
/opt/gitlab/embedded/bin/rake:23:in `'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli/exec.rb:74:in `load'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli/exec.rb:74:in `kernel_load'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli/exec.rb:28:in `run'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli.rb:424:in `exec'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in `invoke_command'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor.rb:387:in `dispatch'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli.rb:27:in `dispatch'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor/base.rb:466:in `start'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli.rb:18:in `start'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/exe/bundle:30:in `block in '
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/friendly_errors.rb:124:in `with_friendly_errors'
/opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/exe/bundle:22:in `'
/opt/gitlab/embedded/bin/bundle:23:in `load'
/opt/gitlab/embedded/bin/bundle:23:in `'
Tasks: TOP => gitlab:backup:db:create