oxygen-settings: 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/oxygen-settings - from package: kde-style-oxygen

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

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