dnapenny: 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/lib/phylip/bin/dnapenny - from package: phylip

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

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