btt: 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/btt - from package: blktrace

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

On Debian possible default full paths are:

/usr/bin/btt - from package: blktrace

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

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