unit2: 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/unit2 - from package: python-unittest2

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

On Debian possible default full paths are:

/usr/bin/unit2 - from package: python-unittest2

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

Error in other languages:
unit2: bevel nie gevind nie
unit2: comandă negăsită
unit2: comando não encontrado
unit2: commande introuvable
unit2: command not found
unit2: käsku ei ole
unit2: không tìm thấy lệnh
unit2: komanda nerasta
unit2: Kommando nicht gefunden.
unit2: kommandot finns inte
unit2: komut yok
unit2: nie znaleziono polecenia
unit2: níor aimsíodh an t-ordú
unit2: no se encontró la orden
unit2: no s'ha trobat l'ordre
unit2: opdracht niet gevonden
unit2: parancs nem található
unit2: perintah tidak ditemukan
unit2: príkaz nenájdený
unit2: příkaz nenalezen
unit2: команда не найдена
unit2: командата не е открита
unit2: 命令找不到
unit2: コマンドが見つかりません