You have already activated rack 1.3.2, but your Gemfile requires rack 1.2.3.

Hi, guys,
I got the below error message when i typed this command in terminal “rackup config.ru” , the file config.ru is rails 's configuration file.

You have already activated rack 1.3.2, but your Gemfile requires rack 1.2.3. Consider using bundle exec. (Gem::LoadError)

So, how should i do , thanks a lot.

That happens because you have rackup 1.3.2 installed and your
application is "locked" at rack 1.2.3

You can use "bundle exec rackup config.ru" to workaround that.

Alternatively, run “bundle install --binstubs”, and then run your various commands with “./bin/$COMMAND”

Both of good answers, thanks a lot.

Oh my god, i need more help when i type this command ‘thin strat’ to start the web server, it still show me this error message.