earthtrack: 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/earthtrack - from package: predict

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

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