olsrd-gui: command not found

Have You tried accessing the binary with the full path?

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/olsrd-gui - from package: olsrd-gui

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