You can check the version of Raspberry Pi OS (formerly Raspbian) that is currently installed on your Raspberry Pi by using the command cat /etc/os-release. This command will display a file called os-release, which contains information about the operating system, including the version number.
Alternatively, you can use the command lsb_release -a, this command will show you the version of the Linux distribution and other related information.
Here’s an example of the output you might see:
PRETTY_NAME="Raspbian GNU/Linux 10 (buster)"
NAME="Raspbian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"
You can see that the version is 10 (buster)
Additionally, you can also use the command uname -a to see the version of the kernel, uname command gives information about the system and the kernel.
Please keep in mind that this is a general command and the output may change depending on the version of Raspberry Pi OS you are using.