install_plugin: 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/share/torrus/bin/install_plugin - from package: torrus-common

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

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