fbpanel: 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/fbpanel - from package: fbpanel

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

On Debian possible default full paths are:

/usr/bin/fbpanel - from package: fbpanel

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

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