dtop: 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
/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/sbin/dtop - from package: diod

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