par: 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/par - from package: par2cmdline

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

On Debian possible default full paths are:

/usr/bin/par - from package: par

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

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