gspectrum: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/gspectrum - from package: gcu-bin

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