dpm-modifypool: 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/dpm-modifypool - from package: dpm

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

On Debian possible default full paths are:

/usr/bin/dpm-modifypool - from package: dpm

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

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