dtfits: 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/dtfits - from package: qfits-tools

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

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