vios-proxy-guest: 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/vios-proxy-guest - from package: vios-proxy-guest

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

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