elk-spacegroup: 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 CentOS possible default full paths are:

/usr/bin/elk-spacegroup - from package: elk-common

You may install the required package with command yum install {package}

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