If you do not have
wget installed, you can install it in Debian or Ubuntu by opening the terminal and run:
sudo apt-get install wget. On CentOS/RHEL 5/6/7,
wget can be installed by running
sudo yum install wget. Once it is installed, websites can be copied using the following command:
wget --mirror --convert-links --adjust-extension --page-requisites --no-parent --wait=0.1 --random-wait https://www.example.com/pages/
Of course, replace the example URL with the address of the website you wish to mirror. Running the command will create a new directory in your current working directory. That new directory will contain the copied website once the mirroring is complete.
Offline copies of websites containing software documentation are especially useful, because they eliminate the need to go through search engines to find the documentation's homepage. One disadvantage of offline documentation is the lack of search functionality. You can overcome that by using desktop search tools like
recoll that are able to search HTML. So far, I've only been using
wget to mirror documentation, but I suppose it could be useful for copying news sites and blogs too.