Make ubuntu system into iso image file

Use Ubuntu's own command mkisofs to make iso files, the specific method is as follows:

1. If you are pressing iso files directly from cd, execute
   sudo umount /dev/cdrom
   dd if=/dev/cdrom of=file.iso bs=1024
2. If you want to press a certain file or directory into the iso file, you need to use the mkisofs tool. This tool is very powerful and can also compress iso in DVD format. You can modify the parameters you want, and there is also the -gui parameter. The simplest usage is as follows:
   mkisofs -r -o file.iso your_folder_name/
3. If you want to install cool to generate an MD5 file, execute
   md5sum file.iso > file.iso.md5
4. If you want to burn an iso file, it's easier. Right-click on this file, and do you see it? There is a burning option (write to disc...), click this option, and then select the disc directory to burn.