compute_relabel: 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
/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/sbin/compute_relabel - from package: selinux-utils

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