fping: 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/sbin/fping - from package: fping

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

On Debian possible default full paths are:

/usr/bin/fping - from package: fping

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

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