reset admin password issue

[alamin]

Hi,

I am trying admin password reset after clean install,
cd /etc/fusionpbx/
mv config.conf config.conf-old
chmod -R 755 /etc/fusionpbx/
chown -R www-data:www-data /etc/fusionpbx/

then going to web install process

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then collect database.0.password = MsDd24AF7iQ2Cc4Y4Eg3M1joU from config.conf-old file.

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then click install for next page.
I see error write permission as like below.

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What can I do now for reset admin password reset?

Please give me some idea.