alter system command

hi,

I have set archive_command like below:

alter system set archive_command ='pgbackrest --stanza=main archive-push %';

then I reloaded the conf file

select pg_reload_conf();

now when i checked it using the show command like it gave me correct output

postgres=# show archive_command;
archive_command
-----------------------------------------
pgbackrest --stanza=main archive-push %

but...

while checking the postgresql.conf file it didn't show me above
output, the parameter acrhive_command is still set with default value

archive_command = '/bin/true/' # command to use to archive a
logfile segment

So please help me in giving the reason of it that even after reloading
the conf file why it didn't set the value in postgresql.conf file ?

Regards,
Atul