sdb: 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 Debian possible default full paths are:

/usr/bin/sdb - from package: sdb

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

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