Error in upgrade Ubuntu 20.04.3 LTS [duplicate]

A solution to this locking problem is detailed in the wiki:

sudo fuser -v /var/cache/debconf/config.dat

Will show you what process is holding the lock:

                     USER        PID ACCESS COMMAND
/var/cache/debconf/config.dat:
                     root      18210 F.... dpkg-preconfigu

Then you simply need to note down the PID and kill it like so:

sudo kill PID
sudo kill -9 PID  # if the first doesn't work

This is more simple one command

I just did:

sudo rm /var/cache/debconf/*.dat 

After I run the apt-get install and (I was installing curl ) and it worked restored the db manual pages.

PS: I removed something with apt-get and I did have this problem. but solved it simply thank also to @rajagenupula

1. open your terminal
2. open the location /var/cache/debconf with gksu nautilus
3. move (cut/paste) all of the .dat files to another backup directory.
4. attempt to run again (will likely get a different error)
5. restore those dat files from the aforementioned backup directory.
6. Then try again what you were doing (should work this time).