rel2gpx: 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/rel2gpx - from package: rel2gpx

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

Error in other languages:
rel2gpx: bevel nie gevind nie
rel2gpx: comandă negăsită
rel2gpx: comando não encontrado
rel2gpx: commande introuvable
rel2gpx: command not found
rel2gpx: käsku ei ole
rel2gpx: không tìm thấy lệnh
rel2gpx: komanda nerasta
rel2gpx: Kommando nicht gefunden.
rel2gpx: kommandot finns inte
rel2gpx: komut yok
rel2gpx: nie znaleziono polecenia
rel2gpx: níor aimsíodh an t-ordú
rel2gpx: no se encontró la orden
rel2gpx: no s'ha trobat l'ordre
rel2gpx: opdracht niet gevonden
rel2gpx: parancs nem található
rel2gpx: perintah tidak ditemukan
rel2gpx: príkaz nenájdený
rel2gpx: příkaz nenalezen
rel2gpx: команда не найдена
rel2gpx: командата не е открита
rel2gpx: 命令找不到
rel2gpx: コマンドが見つかりません