pcp-summary: 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/libexec/pcp/bin/pcp-summary - from package: pcp

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

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