1. Download the package via command line by executing this command : wget http://wllbg.org/latest-v2-package && tar -xvf latest-v2-package.
2. manually fill in the details of the database in /app/config/parameters.yml (change database driver to pdo_mysql,since the default is pdo_sqlite).
3. then run php bin/console wallabag:install --env=prod on the console.(it is needed to populate the database).
4. if the prompt asks database already exists, would you like to reset it ? press N(No).
5. would you like to create a new admin user press Y(yes).
6. then fill in  admin username, password and email address and then take the dump.
7. symlinks to $__settings['softpath'].'/vendor/fabpot/php-cs-fixer/php-cs-fixer and $__settings['softpath']./vendor/phpunit/phpunit/phpunit are broken in this version (2.0.5). Please do check it in the next version.
8. Upgrade is not possible from 1.x branch to 2.x due to major changes in database and structure described here :
http://doc.wallabag.org/en/master/user/migration.html
9. We have given upgrade from 2.1.3. In case if there is any change in database then make changes in upgrade.php check them here :
http://doc.wallabag.org/en/master/user/upgrade.html
10. migration is not possible from 2.1.x branch to 2.2.x due to major changes in database and structure described here : http://doc.wallabag.org/en/master/user/query-upgrade-21-22.html. (We have asked developer to provide some patch to run queries.) Once update/migration works plz change <min_require>2.2.0</min_require> in info.xml to older version from where update works.
11. PHP REQUIREMENT LINK : https://doc.wallabag.org/admin/installation/requirements/
12. Take care of symlinks and update in clone as well
13. Check upgrade for every new version from it's supported version and make changes accordingly. https://doc.wallabag.org/en/admin/upgrade.html
14. Keep the realname in `name` field of `[[dbprefix]]user` table in our sql.
15. We have disabled upgrade in 2.6.x as it was throwing error on visiting admin panel post upgrade. Check in next version and enable for 2.6.x version atleast if it's not working for 2.5.x
https://github.com/wallabag/wallabag/issues/6758
16. We have enable upgrade for 2.6.x version itself as for 2.5.x upgrade is not working