dan: 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/dan - from package: emboss

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

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