cain: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/cain - from package: cain

You may install the required package with command apt-get install {package}
Error in other languages:
cain: bevel nie gevind nie
cain: comandă negăsită
cain: comando não encontrado
cain: commande introuvable
cain: command not found
cain: käsku ei ole
cain: không tìm thấy lệnh
cain: komanda nerasta
cain: Kommando nicht gefunden.
cain: kommandot finns inte
cain: komut yok
cain: nie znaleziono polecenia
cain: níor aimsíodh an t-ordú
cain: no se encontró la orden
cain: no s'ha trobat l'ordre
cain: opdracht niet gevonden
cain: parancs nem található
cain: perintah tidak ditemukan
cain: príkaz nenájdený
cain: příkaz nenalezen
cain: команда не найдена
cain: командата не е открита
cain: 命令找不到
cain: コマンドが見つかりません