I only allowed 4G for swap, maybe arch enabled zram and it used 8GB by default and I actually don't need to create a swap partition?
Arch doesn't really do anything you don't tell it to do during installation.
That's the entire point. After installing Arch, you know what your system does, cause you configured it.
You can try using # du -h -d 1 / to locate the largest directory under /. Once you've located the largest directory, replace / with that directory. Repeat that until you find the culprit (if there is a single large directory).
EDIT (2024-07-22T19:34Z): As suggested by @DarkThoughts@fedia.io, you can also use a program like Filelight, which provides a visual and more comprehensive breakdown of the sizes of directories.
Whoops! You are correct — I have updated the original comment. I'm not sure why I wrote df instead of du. This is a good example of why one should always be wary of blindly copying commands 😜 It begins to teeter on being potentially disastrous if I had instead wrote dd.
It's "Steam" inside .local eat up 6GB even though I have not open it yet and tmp files (almost 5GB) that is not clear itself after installing the OS
Ah, I see. Just be aware that any additional file size when you get to the stage you can install KDE is pretty much considered the "bloat" part of installs, meaning you only make arch as bloated as you want after that. I like filelight in KDE https://apps.kde.org/filelight/
Keep in mind that a part of the filesystem will be reserved on creation. Here if I create a completely empty ext4 filesystem with:
truncate -s 230G /tmp/img
mkfs.ext4 /tmp/img
mount /tmp/img /mnt
Dolphin reports "213.8 GiB free of 225.3 GiB (5% used)"
sounds ok for me if you install the full KDE Plasma + all applications package group and add some basic software like LibreOffice