openteacher: 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/openteacher - from package: openteacher

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

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