xgnokii: 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/xgnokii - from package: xgnokii

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

On Debian possible default full paths are:

/usr/bin/xgnokii - from package: xgnokii

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

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