dpm-reservespace: 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-reservespace - from package: dpm

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

On Debian possible default full paths are:

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

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

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