Centos 7 64

What exactly happened "a couple of days ago" – did you upgrade MariaDB? Did you reconfigure something, for example your tmp dir?
Are you able to start other (non-MariaDB) services via systemd?

I have Centos on automatic update. My guess is that Systemd got an update.
I installed version 5.5 and it starts, but I was working with version 10.X
I can give you access to the box and remove the current version 5.5.
The command systemctl start mriadb fails immediately.

5.5 doesn't use systemd, it's irrelevant.
If you want to give us access to the machine, my public SSH key is here: https://launchpad.net/~elenst/+sshkeys

No news about this? I had to start using Fedora 22 and go down one step in MariaDB version.
But somebody needs to fix this issue, it affects millions of users.

philip_38,
Exactly the fact that we are not getting other similar complaints suggests that it's configuration-specific.
We can't have news unless you either provide the access to the machine as you earlier offered, or, for starters, answer the questions from my first comment.

I don't want to post the IP here, kindly send me an email private. I already sent you one last night, but it was probably an old email of yours.
There are no more complaints because nobody upgraded Centos yet.
my email is venefax@gmail.com
Note: there is no configuration at all in my case. a blank new install, with all packets erased, reproduces the issue.

Yours
Federico

Thanks, I've found your email now. I guess it didn't look legit enough so it went to spam. I'll check your instance shortly.

Dear Elena
Kindly add the file /etc/yum.repos,d/maria.repo
for the latest 10.22 version, and install it
then simply
systemctl start mariadb

philip_38,

I've just tried installing on your machine, I don't have a problem with either 10.1.18 or 10.2.2. I've left 10.2.2 installed, check it out.

Dependency Installed:

  MariaDB-client.x86_64 0:10.2.2-1.el7.centos                  MariaDB-common.x86_64 0:10.2.2-1.el7.centos                  MariaDB-compat.x86_64 0:10.2.2-1.el7.centos                 

Complete!

# systemctl start mariadb

# ps -ef | grep mysqld

mysql     7842     1  4 12:36 ?        00:00:00 /usr/sbin/mysqld

root      7874  6976  0 12:36 pts/11   00:00:00 grep --color=auto mysqld

# mysql -uroot -e "select @@version"

+----------------+

| @@version      |

+----------------+

| 10.2.2-MariaDB |

+----------------+

# 

The reporter confirmed via email that the problem is gone; whatever the reason was, apparently it has already disappeared.