before i start upgrading i would like to know if it is possible to upgrade from 1.7.5 to 1.9.0?
Yes it is, you can switch to v1.9.x and run ./nodebb upgrade
0.7.3 -> 0.9.x
git fetch fails when trying to upgrade 0.9.3 -> 0.9.4
Problem after upgrading to 0.9.0 from 0.6.1
How to update mongo data from 0.5.0 to 0.6.1?
Solved Errors upgrading from 1.1.0 to 1.1.2
[SOLVED] Upgrading NodeBB 0.6.0 to 0.7.0+
Crash after 0.6.4 -> 0.7.0
Start fails with UnhandledPromiseRejectionWarning on plain 1.3.0 and 1.4.0