elki-cli: 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/elki-cli - from package: elki

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

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