pmwebd: 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/pmwebd - from package: pcp-webapi

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

On Debian possible default full paths are:

/usr/lib/pcp/bin/pmwebd - from package: pcp-webapi

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

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