blktrace: 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/blktrace - from package: blktrace

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

On Debian possible default full paths are:

/usr/sbin/blktrace - from package: blktrace

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

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