cap: command not found

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

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

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/cap - from package: capistrano

You may install the required package with command apt-get install {package}

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