par2: 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/par2 - from package: par2cmdline

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

On Debian possible default full paths are:

/usr/bin/par2 - from package: par2

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

Error in other languages:
par2: bevel nie gevind nie
par2: comandă negăsită
par2: comando não encontrado
par2: commande introuvable
par2: command not found
par2: käsku ei ole
par2: không tìm thấy lệnh
par2: komanda nerasta
par2: Kommando nicht gefunden.
par2: kommandot finns inte
par2: komut yok
par2: nie znaleziono polecenia
par2: níor aimsíodh an t-ordú
par2: no se encontró la orden
par2: no s'ha trobat l'ordre
par2: opdracht niet gevonden
par2: parancs nem található
par2: perintah tidak ditemukan
par2: príkaz nenájdený
par2: příkaz nenalezen
par2: команда не найдена
par2: командата не е открита
par2: 命令找不到
par2: コマンドが見つかりません