KMail has stopped working. "Akonadi not operational"

[vsmmath]

KMail is the default mail handler. No other setting changes were made, now I have made changes to some default programmes.

Kmail gives an error:
"The Akonadi personal information management service is not operational."
below Red label with X mark on it. Below is Details...... When I click "Details" label: I get the same message Akonadi personal information manager is not operational

[GreyGeek]

In msg #5 you posted:

2016-09-25T06:18:01.783233Z 0 [Warning] 'NO_AUTO_CREATE_USER' sql mode was not set.
2016-09-25T06:18:01.783291Z 0 [Warning] Insecure configuration for --secure-file-priv: Current value does not restrict location of generated files. Consider setting it to a valid, non-empty path.
2016-09-25T06:18:01.783343Z 0 [Note] /usr/sbin/mysqld (mysqld 5.7.15-0ubuntu0.16.04.1) starting as process 2291 ...

2016-09-25T06:18:01.789853Z 0 [Warning] Can't create test file /home/muglurmat/.local/share/akonadi/db_data/muglurmat-desktop.lower-test
2016-09-25T06:18:01.789917Z 0 [Warning] Can't create test file /home/muglurmat/.local/share/akonadi/db_data/muglurmat-desktop.lower-test
2016-09-25T06:18:01.789941Z 0 [ERROR] Fatal error: Please read "Security" section of the manual to find out how to run mysqld as root!

2016-09-25T06:18:01.789964Z 0 [ERROR] Aborting

2016-09-25T06:18:01.789995Z 0 [Note] Binlog end
2016-09-25T06:18:01.790085Z 0 [Note] /usr/sbin/mysqld: Shutdown complete"
exit code: 1
process error: "Unknown error"

That you cannot create "test file"s suggests that you have a permissions problem. Check in ~./local/share/akonadi/db_data to see if muglurmat-desktop.low-test exists and if it does what permissions it and the akonadi/db_data directories have.

One way you can approach this problem is to purge my_sql and KMail from your system, then reinstall KMail. It should bring in my_sql and an other additional packages.

When you uninstall a package you should be careful to make sure it doesn't drag along other parts of the KDE desktop, as some packages often do. If that happens you can re-install the KDE metadesktop package, which will restore mission packages.

[vsmmath]

One way you can approach this problem is to purge my_sql and KMail from your system, then reinstall KMail. It should bring in my_sql and an other additional packages.

Purged my_sql and KMail from system.
Reinstalled Kmail, anxiously clicked on KMail ........ same result. Akonadi is not operational

In a situation like this as a newbie I would have re-installed OS. but after your suggestion reinstalling is never a solution, this has become a challenge. I want to know what has gone wrong.

[Snowhog]

How are you performing your package management; the updating of installed package? If you are using the command line (konsole), what commands are you using?

What repositories are you using?

[vsmmath]

How are you performing your package management; the updating of installed package? If you are using the command line (konsole), what commands are you using?

What repositories are you using?

sudo apt-get purge mysql-server mysql-client mysql-common mysql-server-core-5.5 mysql-client-core-5.5
sudo rm -rf /etc/mysql /var/lib/mysql
sudo apt-get autoremove
sudo apt-get autoclean

KMail i removed using Synaptic package manager.

After re-install it did not work. This was at 3:30 in the morning. I gave feed back here and slept. Got up now, switched on the system, got a message Akonadi is requesting for pass word !
Entered password and KMail is working. Problem solved. Thanks you for reading my attempts to correct the problem.

GreyGeek, Thanks for the guidance. Now I will configure mail ID and start download of emails.

[GreyGeek]

Great!

Also, Muon's problem with the one-off search has been fixed and now it works the way it always has, perfectly, so there is little need to re-install Synaptic.

[vsmmath]

Thank you GreyGeek,
your guidance was really kept me going. I have installed Muon, had not tried recently.