spectool_gtk: 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/spectool_gtk - from package: spectools

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

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