resperf: 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/resperf - from package: dnsperf

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

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