mysql master slave replication on same machine - Can log_bin need point to the same location on both instances?

Question

I have been trying to setup a mater-slave replication on the same machine using mysqld_multi and it does appear to be working, but I have a few questions which have never really been an issue before when running on different machines, so, if I first include both my cnf files for the master and slave respectively;

for the master;

[mysqld1]

user            = mysql
pid-file        = /var/run/mysqld/mysqld_master.pid
socket          = /var/run/mysqld/mysqld_master.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql_master
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking

bind-address            = 127.0.0.1    

key_buffer_size         = 16M
max_allowed_packet      = 16M
thread_stack            = 192K
thread_cache_size       = 8
myisam_recover_options  = BACKUP

query_cache_limit       = 1M
query_cache_size        = 16M

log_error = /var/log/mysql/error_master.log

server-id               = 1
log_bin                 = /var/log/mysql/mysql-bin.log
expire_logs_days        = 10
max_binlog_size   = 100M
#binlog_do_db           = include_database_name
innodb_flush_log_at_trx_commit  = 1
sync_binlog                 = 1
binlog-format               = ROW

character-set-server  = utf8mb4
collation-server      = utf8mb4_general_ci

and for the slave;

[mysqld2]

user            = mysql
pid-file        = /var/run/mysqld/mysqld_slave.pid
socket          = /var/run/mysqld/mysqld_slave.sock
port            = 3307
basedir         = /usr
datadir         = /var/lib/mysql_slave
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking

bind-address            = 127.0.0.1

key_buffer_size         = 16M
max_allowed_packet      = 16M
thread_stack            = 192K
thread_cache_size       = 8
myisam_recover_options  = BACKUP

query_cache_limit       = 1M
query_cache_size        = 16M

log_error = /var/log/mysql/error_slave.log
server-id               = 2
log_bin                 = /var/log/mysql/mysql-bin.log
expire_logs_days        = 10
max_binlog_size   = 100M
#binlog_do_db           = include_database_name
#binlog_ignore_db       = exclude_database_name
relay-log               = /var/log/mysql/relay-bin
#relay-log-index                = /var/log/mysql/relay-bin.index
#master-info-file       = /var/log/mysql/master.info
#relay-log-info-file    = /var/log/mysql/relay-log.info

character-set-server  = utf8mb4
collation-server      = utf8mb4_general_ci

1. Does the log_bin need to point to different files on both instances? (you'll see here, mine does not).

2. What does the following do (from the master);

   innodb_flush_log_at_trx_commit = 1

   sync_binlog = 1

   binlog-format = ROW

Below is a SHOW SLAVE STATUS\G;

MariaDB [(none)]> show slave status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 127.0.0.1
                  Master_User: replication
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000016
          Read_Master_Log_Pos: 780
               Relay_Log_File: relay-bin.000004
                Relay_Log_Pos: 756
        Relay_Master_Log_File: mysql-bin.000016
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 780
              Relay_Log_Space: 1048
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos: 
      Replicate_Do_Domain_Ids: 
  Replicate_Ignore_Domain_Ids: 
                Parallel_Mode: conservative
1 row in set (0.00 sec)

Answer 1

No. Keep everything separate, including my.cnf, log files, port, socket, data, etc. Be sure to have a different server_id for each.

Better yet, put them in different VMs (or use Docker). There will still be things that you must be sure to keep separate: data, port numbers, and possibly other things.