Cygwin as-distributed provides a rather unique, and sometimes inconvenient, mechanism for installation. A small network-install executable is provided, which consults online repositories for downloads of installation artifacts. The install executable also relies on locally-written meta-data to keep track of the entire installation footprint.

• Uninstall all services
  • List services installed: cygrunsrv -L
    NOTE: the inetd service won't show in the list, even if installed/running, but stopping it and removing it will work regardless
  • Stop each service with: cygrunsrv –stop service_name
  • Remove each service with: cygrunsrv –remove service_name
• Stop X server, after stopping any cygwin X clients that are running
• If using the cyglsa authentication mechanisms (hopefully not - pain), revert all of that
• Remove the cygwin (or cygwin64) folder tree
• Remove all shortcuts installed by the installer
• Remove references to the cygwin folder tree from environment variables (most notably, PATH)
• Using the regedit program, remove the registry tree(s) Software\Cygwin under HKEY_LOCAL_MACHINE and/or HKEY_CURRENT_USER

Cygwin makes a particularly powerful solution for a client-side agent in providing central command-n-control with a centralized backup/archival system. Here are some details around how Albert Lea Data has devised such a solution.

• Create an administrative user (we'll refer to as $USR) for the backup system identity to be used, log into Windows as that user
• Acquire the ZIP archive to the client machine: http://www.albertleadata.org/pub/backup-client-agent.zip
• Extract the contents of the ZIP archive to a working location
• Move the cygwin64 folder extracted from the ZIP archive to suitable destination, we'll refer to as $CYGDIR (either c:\ or d:\ recommended)
• Edit the .reg files extracted from the ZIP archive to ensure path references are corrected
• Right-click on each .reg file and choose Merge
• Right-click on the Cygwin.bat batch file in the $CYGDIR folder and choose Run as administrator
• Run these commands:

  mkpasswd -l > /etc/passwd
  mkgroup -l > /etc/group
  chmod 111 /var
  chmod +t /var
  ssh-host-config

  Make sure to enter ntsec for CYGWIN value, and specify your new admin user when prompted

• Start the SSH service: cygsrvrun -S sshd
• SSH to the Windows box and log in as new admin user
• Create SSH key with: ssh-keygen -t rsa … make sure to specify empty passphrase
• Populate authorized_keys file with server's SSH key for password-less operation
• Populate backup server's host key (typically just SSH to it and answer yes at key prompt)
• Ensure home directory has group-write disabled, for example: chmod g-w ~

This is the recipe for how the client-side agent footprint is bundled, and how to go about upgrading it.