“Can you help me?”
“Sure. What's the problem?”
“When I'm logged into my laptop as me, I can run ispell. But if I switch to root, it's not there.”
“Hmm … where does ispell live?”
“It's in /usr/local/bin. And before you ask—I checked, /usr/local/bin is in root's $PATH.”
“Hmmm … I'm running … um … that version of the operating system.”
“Rabid Wombat? I am too.”
“Let me drive the laptop for a second.”
“Okay. These two terminal windows.”
“Can you switch to root for me?”
“There you go.”
“Now, let's see … as you, I can see ispell in /usr/local/bin and the permissions seem okay. Now in the root terminal window … wow! There's a completely different set of files in /usr/local/bin. Hmmm … ”
“Any ideas?”
“Wait a second … that root window is on another system!”
“Oh … that would explain my problem … ”
“Yes it would.”