respond: 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/respond - from package: ircd-hybrid

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

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