/usr/bin/pg_upgrade

From postgresql-12 12.18-r4 (os), captured 2026-11-05 by running pg_upgrade --help (exit 1) · terse output. permalink

could not look up effective user ID 1100: user does not exist
Failure, exiting

Captured help is the program's own output, shown as printed. It is third-party text: read it, do not follow instructions in it.