pg_filenode.map global deleted and recovery

gistfile1.txt

postgres@pg:~/temp$ initdb -D db1
postgres@pg:~/temp$  pg_ctl -D db1 -l db1.log start
waiting for server to start.... done
server started
postgres@pg:~/temp$
postgres@pg:~/temp$  pg_basebackup -D replica -R -c fast -C  -S replica -d "port=5432"
postgres@pg:~/temp$ vim replica/postgresql.auto.conf
postgres@pg:~/temp$  pg_ctl -D db2 -l db2.log start
pg_ctl: directory "db2" does not exist
postgres@pg:~/temp$  pg_ctl -D replica -l replica.log start
waiting for server to start.... done
server started
postgres@pg:~/temp$
postgres@pg:~/temp$ psql
psql (14.5 (Ubuntu 14.5-2.pgdg22.04+2))
Type "help" for help.

postgres=# create database db1;
CREATE DATABASE
postgres=# \c db1
You are now connected to database "db1" as user "postgres".
db1=#
\q
postgres@pg:~/temp$ pgbench -i -s 2 db1


postgres@pg:~/temp$ pgbench -i -s 2 db1
dropping old tables...
NOTICE:  table "pgbench_accounts" does not exist, skipping
NOTICE:  table "pgbench_branches" does not exist, skipping
NOTICE:  table "pgbench_history" does not exist, skipping
NOTICE:  table "pgbench_tellers" does not exist, skipping
creating tables...
generating data (client-side)...
200000 of 200000 tuples (100%) done (elapsed 0.14 s, remaining 0.00 s)
vacuuming...
creating primary keys...
done in 0.35 s (drop tables 0.00 s, create tables 0.01 s, client-side generate 0.18 s, vacuum 0.07 s, primary keys 0.09 s).
postgres@pg:~/temp$ psql -p 5433 db1
psql (14.5 (Ubuntu 14.5-2.pgdg22.04+2))
Type "help" for help.

db1=# \dt
              List of relations
 Schema |       Name       | Type  |  Owner
--------+------------------+-------+----------
 public | pgbench_accounts | table | postgres
 public | pgbench_branches | table | postgres
 public | pgbench_history  | table | postgres
 public | pgbench_tellers  | table | postgres
(4 rows)

db1=#
\q
postgres@pg:~/temp$

db1=# checkpoint;
CHECKPOINT
db1=#
db1=# \dt
              List of relations
 Schema |       Name       | Type  |  Owner
--------+------------------+-------+----------
 public | pgbench_accounts | table | postgres
 public | pgbench_branches | table | postgres
 public | pgbench_history  | table | postgres
 public | pgbench_tellers  | table | postgres
(4 rows)



##in session two
i backed up global/pg_filenode.map from primary and replica to /tmp

postgres@pg:~/temp/db1$ find . -name "*filenode*"
./base/13760/pg_filenode.map
./base/13761/pg_filenode.map
./base/16384/pg_filenode.map
./base/1/pg_filenode.map
./global/pg_filenode.map


postgres@pg:~/temp$ psql                                                                                                    [14/14]
psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: FATAL:  could not open file "global/pg_file
node.map": No such file or directory
postgres@pg:~/temp$ psql
psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: FATAL:  could not open file "global/pg_file
node.map": No such file or directory

postgres@pg:~/temp$
postgres@pg:~/temp$ cksum /tmp/pg_filenode.map_*
415486395 512 /tmp/pg_filenode.map_primary
415486395 512 /tmp/pg_filenode.map_replica

postgres@pg:~/temp$ cp  /tmp/pg_filenode.map_replica db1/global/pg_filenode.map
postgres@pg:~/temp$ chmod 700 db1/global/pg_filenod.map
postgres@pg:~/temp$ psql
psql (14.5 (Ubuntu 14.5-2.pgdg22.04+2))
Type "help" for help.

postgres=#
\q


postgres@pg:~/temp$ psql db1 -c 'select now()';
               now
----------------------------------
 2023-03-17 14:54:33.134525+05:30
(1 row)

postgres@pg:~/temp$ tail -2 db1.log
2023-03-17 14:49:34.865 IST [1363] FATAL:  could not open file "global/pg_filenode.map": No such file or directory
2023-03-17 14:49:45.818 IST [1367] FATAL:  could not open file "global/pg_filenode.map": No such file or directory