bt-adapter: 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/bt-adapter - from package: bluez-tools

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

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