mariaDB starting error

Hello,

I am currently triing to use MySQL on a Yocto based distribution.
My yocto branch is pyro and my target is imx7. Just for information I am using this repository https://github.com/varigit/variscite-bsp-platform.git

I have added ${bindir}/mysqld_safe_helper to FILES_${PN}-server on meta-openembedded/meta-oe/recipes-support/mysql/mariadb.inc

I am using 0001-disable-ucontext-on-musl.patch patch as recommended by post : https://jira.mariadb.org/browse/MDEV-14044

I generated the image and I tried to boot with his new image, but I got the following error:

**180130 20:00:37 [Note] /usr/sbin/mysqld (mysqld 5.5.55-MariaDB) starting as process 916 ...
180130 20:00:38 [Note] /usr/sbin/mysqld (mysqld 5.5.55-MariaDB) starting as process 925 ...

PLEASE REMEMBER TO SET A PASSWORD FOR THE MariaDB root USER !
To do so, start the server, then issue the following commands:

'/usr/bin/mysqladmin' -u root password 'new-password'
'/usr/bin/mysqladmin' -u root -h imx7-var-som password 'new-password'

Alternatively you can run:
'/usr/bin/mysql_secure_installation'

which will also give you the option of removing the test
databases and anonymous user created by default. This is
strongly recommended for production servers.

See the MariaDB Knowledgebase at http://mariadb.com/kb or the
MySQL manual for more instructions.

Please report any problems at http://mariadb.org/jira

The latest information about MariaDB is available at http://mariadb.org/.
You can find additional information about the MySQL part at:
http://dev.mysql.com
Consider joining MariaDB's strong and vibrant community:
https://mariadb.org/get-involved/

done.
Starting MySQL.180130 20:00:39 mysqld_safe Logging to '/var/log/mysqld.err'.
180130 20:00:39 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
/usr/bin/mysqld_safe_helper: Can't create/write to file '/var/log/mysqld.err' (Errcode: 13)
ERROR!
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Do you have any suggestion please?

Regards.