illumread: 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/illumread - from package: argyll

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

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