On my Ubuntu 20 server, I installed PostgreSQL 13 using the apt manager. I read some articles on performance tuning of PostgreSQL  and thought of increasing the WAL segment size (from default of 16MB). I see the following instruction, however, I don't know where to run this.
initdb -D ./data --wal-segment=1024
I guess the documentation refers to installing from PostgreSQL source code, which I don't intend to do. How do I go about change the WAL segment size?
Following Daniel's answer, I did the following steps
$ pg_lsclusters $ sudo pg_dropcluster --stop 13 main $ sudo pg_createcluster 13 main -- --wal-segsize=256 $ sudo pg_ctlcluster 13 main start
You can verify the size of the WAL segments as
# du -hcs /var/lib/postgresql/13/main/pg_wal/*