postgreSQL - psql \i : how to execute script in a given path

Postgres started on Linux/Unix. I suspect that reversing the slash with fix it.

\i somedir/script2.sql 

If you need to fully qualify something

\i c:/somedir/script2.sql

If that doesn't fix it, my next guess would be you need to escape the backslash.

\i somedir\\script2.sql

Have you tried using Unix style slashes (/ instead of \)?

\ is often an escape or command character, and may be the source of confusion. I have never had issues with this, but I also do not have Windows, so I cannot test it.

Additionally, the permissions may be based on the user running psql, or maybe the user executing the postmaster service, check that both have read to that file in that directory.

Try this, I work myself to do so

\i 'somedir\\script2.sql'