pm: 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/pm - from package: powerman

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

On Debian possible default full paths are:

/usr/bin/pm - from package: powerman

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

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