lastb: 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/lastb - from package: sysvinit-tools

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

On Debian possible default full paths are:

/usr/bin/lastb - from package: sysvinit-utils

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

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