tap-ctl: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/sbin/tap-ctl - from package: blktap-utils

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