composite-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/composite-gui - from package: composite

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