proot: 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/proot - from package: proot

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

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