dar: 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/dar - from package: dar

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

On Debian possible default full paths are:

/usr/bin/dar - from package: dar

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

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