Thank you for your prompt response.
Most probably i run update as root that was my mistake.
I followed your instructions but the issue still remain. Any advice?
root@erpnext-vm:/home/erpnext/frappe-bench/apps# chown -R erpnext frappe
erpnext@erpnext-vm:~/frappe-bench/apps/frappe$ git reset --hard
HEAD is now at 383a1e9 Merge pull request #882 from pdvyas/fix-mariadb