Duration#ago and Duration#from_now return ActiveSupport::TimeWithZone, which can introduce unexpected timezone behavior when an app assumes local or timezone-unaware dates.

Webpacker configuration can be hard to inspect when builds misbehave; dumping the environment, using browser or Node debugging, and emitting warnings help reveal the active webpack settings.

Large ZIP downloads can start immediately without writing files to disk, using zip_tricks_stream for custom content or zipline for existing attachments.

Rails 2.3 can return either HTML or JSON from one controller action, but render_to_string inside format.json may trigger ActionView::MissingTemplate.

Bundler’s default release task can publish private gems to rubygems.org; allowed_push_host in gem metadata restricts pushes to a trusted host.

Quickly make one Apache virtual host available at localhost while switching projects. The script disables other sites, can re-enable the default site, and lists available sites without arguments.

WEBrick can emit unreadable URI and request-line errors when a browser connects with HTTPS; switching the URL to http avoids the SSL mismatch.

Growing memory usage in Ruby and Rails can exhaust a process and cause crashes; ObjectSpace.count_objects helps identify leaking object types, and derailed_benchmarks can aid diagnosis.

console-for opens a remote Rails console on a Capistrano deployment target with one command, so staging and other environments can be accessed quickly.

Rails console debugging for mail delivery failures, with ActionMailer settings inspection and a direct test message to verify SMTP and spam score.

Passenger can be configured or upgraded to use Ruby Enterprise instead of MRI, then Apache is restarted with the generated module instructions.

Rails Spring processes can linger and restart unexpectedly, interfering with command runs; stopping the process and disabling auto-start prevents it from coming back.

YARD 0.6 adds the ability to serve documentation for gems as well as the current project with yard server. Just like gem server in RubyGems, you can serve gem docs. The advantage to YARD’s server is that you don’t need to pre-generate the static docs (with a gem install) before running the server. If you installed your gem with --no-rdoc, YARD will just generate it on the fly!

Remote graphical programs can run on your local desktop through SSH, but X11 forwarding is slower and exposes your X session to a trusted host.

Hidden X displays can be inspected by taking a screenshot of the active display, including Xvfb-backed sessions used for headless tests.

Run a Capistrano command across every known deploy target, including staging and production, with geordi cap or geordi capistrano shortcuts.

Inspect raw TCP or UDP data arriving on a port, such as an HTTP request, with nc and redirect the output to stdout or a file.

Ubuntu lets you mount an SSH shell into Nautilus from Places -> Connect to server (select "SSH" as server type).

In order to copy a file over SSH from a shell:

scp filename username@remotehost:

The trailing ":" directs the file to username's home directory on the remote host.

You can also copy a file from the remote host to your local machine:

scp remotehost:remotepath localpath