pingd: 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/pingd - from package: whatsup-pingd

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

On Debian possible default full paths are:

/usr/bin/pingd - from package: echolot

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

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