scheme-elk: 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/scheme-elk - from package: elk

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

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