First to 2.7, then to 3.0, then to 3.4.
Read the release notes for each version very carefully. You will also need to upgrade to PHP 7 but don't do it too soon as earlier versions don't work with PHP 7.
https://docs.moodle.org/dev/Moodle_2.7_release_notes
Just 2 cent notes to Howards response ... due to begining version and destination.
Check addons installed in the 2.4.x for compatibility through the versions to destination. moosh is a handy tool for that.
Any customized code?
After each stage of the 'march', make a backup of code and DB for sure so you don' t loose ground just in case there is a hickup with the next step upwards. Consider the moodledata directory should also be backed up for a full site ... however, on a site that has been used, that directory could be massive and require quite a bit of space to archive at each stage ... so also consider using rsync for moodledata. Minimally, do filedir alone.
Upgrading php to 7.0.x can take place *after* reaching 3.0.highest - not before.
'spirit of sharing', Ken
Not quite, the first Moodle version to support PHP 7 was 3.0.1.
Up until (and including) 3.0 PHP 5.4 was fine. I would upgrade to 3.0 (latest version) THEN upgrade to PHP 7.0. You can upgrade to PHP 7.1 once you have got to 3.4.
It's not the only way to do it. You can go through PHP 5.6 as well. Wrote down the minimum and maximum PHP versions for each Moodle release you intend to upgrade to and see what is best/easiest for you.
Well, may as well add 2 more cents - for what it's worth.
At each stage of the 'march', check server environment in Moodle. Update the component then see what Moodle reports as needing attention - or fixed or whatever ... at the next target version in the 'march'.
Hint: you will see some recommendations for database.
'spirit of sharing', Ken
I have following links as per Howard said.
https://docs.moodle.org/dev/Moodle_2.7_release_notes
https://docs.moodle.org/dev/Moodle_3.0_release_notes
https://docs.moodle.org/dev/Moodle_3.4_release_notes
1. 2.4 To 2.7 and 2.7 To 3.0 = I have to use PHP of 5.5 PHP Version ( I have used temporary PC )
After that I have convert 3.0 to 3.4 with PHP 7.0+ version.
