'lwt.unix' not found

["Yiming Zhang" <sdiris@xxxxxxxxx>]

I followed the wiki instructions to install mirage on Debian Squeeze. However, 
I got the following errors when I arrived at the step "opam --verbose install 
cow mirage-fs". Can anybody can help me solve this problem?

Thanks!
Yiming

--------------------------------------------
ocamlfind: Package `lwt.unix' not found
make[1]: *** [all] Error 2
make: *** [all] Error 2
ocamlfind: [WARNING] No such directory: /root/.opam/system/lib/mirage
[2514] ERROR: Compilation failed with error 2
[2514] ERROR: Globals.Exit(66)
[2506] ERROR: Command failed while installing mirage.0.3dev
  'opam --verbose install cow mirage-fs' failed