gtk-gnutella: 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/gtk-gnutella - from package: gtk-gnutella

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

On Debian possible default full paths are:

/usr/bin/gtk-gnutella - from package: gtk-gnutella

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

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