External hard drive and Spotlight indexing

Spotlight indexing may prevent an external hard drive from being rejected.
The command

sudo lsof | grep /Volumes/Mac\ Backup\ HD/

shows which files on the mounted volume are being accessed.

To disable spotlight, use

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

To enable spotlight,

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist


To disable indexing without turn off spotlight,

mdutil -i off -d /Volumes/REDSTAR