theme: 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/theme - from package: discount

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

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