osgearth_demo: 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/osgearth_demo - from package: osgearth

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

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