How to merge pdf files on Ubuntu ?

First:

sudo apt-get install pdftk

Next:

pdftk file1.pdf file2.pdf cat output mergedfile.pdf

Postgresql sequence reset after table truncation

TRUNCATE TABLE table_name 
RESTART IDENTITY;

How to convert djvu files to pdf on Ubuntu ?

We need "ddjvu" command to convert the files. The following command converts your djvu files into pdf quickly:

ddjvu -format=pdf -quality=80 file.djvu output.pdf

 If you want to see the flow, you can add "-verbose" to end of the above code.

Enjoy!