From Online Manual
The requirements for SMF are higher than the requirements for YaBB SE. To begin the conversion, the user should make sure that the server they intend to use, meets the requirements. Failure to do so may leave them with a broken board.
The requirements for upgrading SMF can be viewed by visiting the following page:
Note that they would be the same requirements as the requirements for installing SMF.
The Change Log
A change log is a list of improvements, bug fixes and corrections that have been made through the various versions of SMF. This is a great reference to see what has been enhanced over the course of development, and a great resource for checking changes.
Versions before SMF 1.1.4 have a changelog.txt file among the files inside the download-able archives. Versions after this require a separate download from the downloads page.
To upload SMF to the server, a user must use a FTP client and initiate a connection to their server. They need to overwrite the old files with the new ones. This step may take time, depending on how fast the user's internet connection is.
Once all the files are uploaded, if they are using a Unix-style server, they will need to change the permissions using CHMOD on a few of the files and directories. The procedure to do this varies between different FTP programs, but generally, the user should right click on the file or directory whose permissions they wish to change, and select Properties > Permissions > CHMOD and enter a number (777 or 755 in this case) in the permissions field. A list of files which need their permissions changed can be found on the installing SMF page.
Beginning the Upgrade
Assuming the previous steps went well, the user should now have the SMF source files on their server and the relevant permissions set. They practically have the new version of SMF already. All that the user needs to do now, is run the upgrade.php file to make the necessary changes in their database structure and their Settings.php file.
To do these things, the user should open their favorite web browser and browse to http://www.usersdomain.tld/forum/upgrade.php. If the user set the permissions correctly on Settings.php and Setting_bak.php and uploaded all the files, they should see a form with the following checkboxes:
* Backup database with the prefix "backup_yourprefix_". Checking this box will cause the SMF upgrade utility to save a copy of the original forum database tables prior to upgrading their structure (it is a good idea for the user to make their own backups anyways.) * Put the Forum into maintenance mode during upgrade. Checking this box will put the forum into maintenance mode during the upgrade process so the forum's users will see a friendly note that the forum is being upgraded, rather than a page full of errors. * Output extra debugging information. Checking this box will cause the upgrade utility to display extra debugging information during the conversion or upgrade process. This is useful if the user experiences problems and they want to report them.
There may also be a "Convert the existing YaBB SE template and set it as default option", which is only shown if the user has an existing template.php from YaBB SE, and they have not already converted it to an SMF-style template. Using this option, when upgrading from YaBB SE, is recommended. It will make the forum, by default, look very similar to how it did before.
Once the user has selected the desired options, they should select the continue link. Depending on the size of the forum, the upgrade process may take a while.
Finishing the Upgrade
The forum should now be successfully converted to SMF and the user can explore the new features and start using their forum; however, before doing so, they MUST delete the upgrade.php file from the server, since leaving it there can be a major security risk. (Anyone could put the forum into maintenance mode!)
To do so, the user needs to return to their FTP program. In the directory that SMF is installed in, the user needs to locate upgrade.php, select it, and select "Delete". They may also be able to check the box that says to delete the upgrade file, without having to delete it through an FTP program, however, this will not work on all servers.