backtracker: 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 CentOS possible default full paths are:

/usr/bin/backtracker - from package: GMT

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/gmt/bin/backtracker - from package: GMT

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

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