portrelease: 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:

/sbin/portrelease - from package: portreserve

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

On Debian possible default full paths are:

/sbin/portrelease - from package: portreserve

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

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