whohas: 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/whohas - from package: whohas

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

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