dar_slave: 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_slave - from package: dar

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

On Debian possible default full paths are:

/usr/bin/dar_slave - from package: dar

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

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