نصب نرم‌افزار

* /etc/apt/sources.list
      deb http://deb.debian.org/debian bullseye main contrib non-free
      deb http://deb.debian.org/debian bullseye-updates main contrib non-free
      deb http://deb.debian.org/debian bullseye-backports main contrib non-free
      deb http://security.debian.org/debian-security bullseye-security main contrib non-free
      deb-src http://deb.debian.org/debian bullseye main contrib non-free
      deb-src http://deb.debian.org/debian bullseye-updates main contrib non-free
      deb-src http://deb.debian.org/debian bullseye-backports main contrib non-free
      deb-src http://security.debian.org/debian-security bullseye-security main contrib non-free

* apt update
* apt upgrade
* apt install tree
* apt search speedometer