Ubuntu 32-bit version has a limitation of using only up to 4GB of RAM. To use more than 4GB RAM on a Ubuntu system, you need to install the 64-bit version of the operating system.
The 64-bit version of Ubuntu can support up to 2^64 bytes (16 exabytes) of RAM.
To check if your system is running a 32-bit or 64-bit version of Ubuntu, you can use the uname -m command.
If the output of the command is x86_64, then you are running a 64-bit version of Ubuntu. If the output is i686 or i386, then you are running a 32-bit version of Ubuntu.
To switch from 32-bit to 64-bit, you will need to perform a fresh installation of the operating system.