lyx contents page numbering

The following is quoted from  https://wiki.lyx.org/FAQ/Numbering#startpage

How can I have roman pagination (i, ii, iii...) for the first part of my document?

• If you use a book class, simply insert
  \frontmatter
  at the beginning of the document. This will switch page numbering to roman (i, ii, iii...)
  \mainmatter
  will switch back to arabic (1, 2, ...) and start from "1".
• With report or article classes, insert at the beginning (in the LaTeX preamble):
  \pagenumbering{roman}
  and then, where you want to switch back (somewhere on the page in the normal text), in ERT (Ctrl-L):
  \pagenumbering{arabic}
  \setcounter{page}{1}

My LyX example:

 

User missing in unity-control-center "Users panel" (Solved strangely)

One day (2020-12-9), I found there are no any user listed in "User panel" inside unity-control-center (also gnome-control-center).  It's sort of frustrated! Google any related terms, found this link:

https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1876460https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1876460

I followed some messages in there to create another system user.  Like this,  ( "joe" was already a user. )

sudo userdel -rf joe
sudo adduser joe
sudo adduser joe sudo 

chiao@kpci7:/etc$ id joe
uid=1000(joe) gid=1003(joe) 群組=1003(joe),27(sudo)

The strange thing happened. I open the "User panel" in unity-control-center again. All the users were back! Like this: