pmmessage: 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/pmmessage - from package: pcp-gui

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

On Debian possible default full paths are:

/usr/bin/pmmessage - from package: pcp-gui

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

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