How do I convert epub to mobi using calibre?

How do I convert epub to mobi using Calibre for this?

Yes, Calibre package contains a script called ebook-convert to convert ebooks between formats. You can install Calibre with

sudo apt-get install calibre

then

ebook-convert "book.epub" "book.mobi"

NB: Other formats are supported, too:

ebook-convert "book.azw3" "book.pdf"

I found a script for batch conversion:

for book in *.epub; do echo "Converting $book"; ebook-convert "$book" "$(basename "$book" .epub).mobi"; done

It works good for me, but the process is pretty slow.

You can also do this without installing Calibre. This would be really handy on a Chromebook, for example. There is a free, online site called EPUB Converter that will let you upload the epub and it lets you then download the mobi equivalent.

Install calibre. Works with any arbitrary folder depth.

find . -name '*.epub' -type f -exec bash -c 'ebook-convert "$0" "${0%.epub}.mobi" --prefer-author-sort --output-profile=kindle --linearize-tables --smarten-punctuation --enable-heuristics' {} \;

Yes, you can use Calibre for epub to mobi conversion. They declare mobi as supported output format in their FAQ.

I don’t think there’s anything Ubuntu-specific in the question, so it would probably belong somewhere else.