Fatal error: Can’t change to run as user ‘mysql’ ; Please check that the user exists!

Problem Statement:

I got the error while starting the server, and is it not able to start as mysql user.
It throws the below error

080915 19:58:10 mysqld started
Fatal error: Can’t change to run as user ‘mysql’ ; Please check that the user exists!
080915 19:58:10 Aborting

080915 19:58:10 /usr/local/mysql4.1.3/bin/mysqld: Shutdown complete

080915 19:58:10 mysqld ended

080915 20:03:59 mysqld started
Fatal error: Can’t change to run as user ‘mysql’ ; Please check that the user exists!
080915 20:03:59 Aborting

080915 20:03:59 /usr/local/mysql4.1.3/bin/mysqld: Shutdown complete

080915 20:03:59 mysqld ended

080915 20:09:07 mysqld started
Fatal error: Can’t change to run as user ‘mysql’ ; Please check that the user exists!
080915 20:09:07 Aborting

080915 20:09:07 /usr/local/mysql4.1.3/bin/mysqld: Shutdown complete

080915 20:09:07 mysqld ended

080915 20:12:21 mysqld started
080915 20:12:21 InnoDB: Started; log sequence number 0 43644
/usr/local/mysql/bin/mysqld: ready for connections.
Version: ‘4.1.3-beta-standard’ socket: ‘/tmp/mysql3311.sock’ port: 3311
080915 20:12:21 Slave SQL thread initialized, starting replication in log ‘hawk-bin.000027′ at position 301237442, relay log
‘./menus-relay-bin.000006′ position: 4
080915 20:12:21 Slave I/O thread: connected to master ‘replicate@x.x.x.90:3306′, replication started in log ‘hawk-bin.
000027′ at position 301237442
080915 20:12:21 Error reading packet from server: Client requested master to start replication from impossible position (ser
ver_errno=1236)
080915 20:12:21 Got fatal error 1236: ‘Client requested master to start replication from impossible position’ from master wh
en reading data from binary log
080915 20:12:21 Slave I/O thread exiting, read up to log ‘hawk-bin.000027′, position 301237442
080915 20:13:07 Aborted connection 4 to db: ‘unconnected’ user: ‘root’ host: `localhost’ (Got an error writing communication
packets)
080915 20:13:07 /usr/local/mysql/bin/mysqld: Normal shutdown

080915 20:13:07 Error reading relay log event: slave SQL thread was killed
080915 20:13:07 InnoDB: Starting shutdown…
080915 20:13:09 InnoDB: Shutdown completed; log sequence number 0 43644
080915 20:13:09 /usr/local/mysql/bin/mysqld: Shutdown complete

080915 20:13:09 mysqld ended

080915 20:23:30 mysqld started
080915 20:23:31 InnoDB: Started; log sequence number 0 43644
/usr/local/mysql/bin/mysqld: ready for connections.
Version: ‘4.1.3-beta-standard’ socket: ‘/tmp/mysql3311.sock’ port: 3311
080915 20:23:31 Slave SQL thread initialized, starting replication in log ‘hawk-bin.000027′ at position 301237442, relay log
‘./menus-relay-bin.000008′ position: 4
080915 20:23:31 Slave I/O thread: connected to master ‘replicate@x.x.x.90:3306′, replication started in log ‘hawk-bin.
000027′ at position 301237442
080915 20:23:31 Error reading packet from server: Client requested master to start replication from impossible position (ser
ver_errno=1236)
080915 20:23:31 Got fatal error 1236: ‘Client requested master to start replication from impossible position’ from master wh
en reading data from binary log
080915 20:23:31 Slave I/O thread exiting, read up to log ‘hawk-bin.000027′, position 301237442
080915 20:34:49 Aborted connection 3 to db: ‘unconnected’ user: ‘root’ host: `localhost’ (Got an error reading communication
packets)
080915 20:35:56 Error reading relay log event: slave SQL thread was killed
080915 20:35:59 Slave SQL thread initialized, starting replication in log ‘hawk-bin.000027′ at position 301237442, relay log
‘./menus-relay-bin.000009′ position: 4

Solution :
The issue was solve by running the server with “sudo - mysql” before the mysql start up script.

sudo -u mysql $BASEDIR/bin/mysqld –defaults-file=$DEFAULT –basedir=$BASEDIR –datadir=$DATADIR \
–user=mysql –pid-file=$PIDFILE 2>&1

Could not parse relay log event entry.

If a slave show the below error then

1) If the slaves relay-log is corrupted, the run the change master to get the slave in sync with master.

2) we have to import a fresh dump from master to get the slave in sync with master if the master’s binlog is corrupted.

Show slave status :

mysql> show slave status\G
*************************** 1. row ***************************
Master_Host: 10.x.x.39
Master_User: replicate
Master_Port: 3307
Connect_retry: 60
Master_Log_File: db-master.077
Read_Master_Log_Pos: 7400184
Relay_Log_File: db-slave-relay-bin.010
Relay_Log_Pos: 150588765
Relay_Master_Log_File: db-master.076
Slave_IO_Running: Yes
Slave_SQL_Running: No
Replicate_do_db: broadbandnew,archive
Replicate_ignore_db:
Last_errno: 0
Last_error: Could not parse relay log event entry. The possible reasons are: the master’s binary log is corrupted (you can check this by running ‘mysqlbinlog’ on the binary log), the slave’s relay log is corrupted (you can check this by running ‘mysqlbinlog’ on the relay log), a network problem, or a bug in the master’s or slave’s MySQL code. If you want to check the master’s binary log or slave’s relay log, you will be able to know their names by issuing ‘SHOW SLAVE STATUS’ on this slave.
Skip_counter: 0
Exec_master_log_pos: 150588671
Relay_log_space: 157989718
1 row in set (0.00 sec)

Duplicate entry for key 1′ on query

If the slave show the following error then skip the same as below.

mysql> show slave status\G
*************************** 1. row ***************************
Master_Host: x.x.4.3
Master_User: replicate
Master_Port: 3307
Connect_retry: 60
Master_Log_File: master.077
Read_Master_Log_Pos: 7394212
Relay_Log_File: slave- relay-bin.010
Relay_Log_Pos: 150588010
Relay_Master_Log_File: master.076
Slave_IO_Running: Yes
Slave_SQL_Running: No
Replicate_do_db: bandnew,archive
Replicate_ignore_db:
Last_errno: 1062
Last_error: Error ‘Duplicate entry ‘122453106710.31.87.80-mdazaz123-2008-10-21 03:38:23′ for key 1′ on query. Default database: ‘bandnew’. Query:

‘insert into br_info(UI_ID,UI_USER,CD_CAF,BI_PRODUCT,BI_STIME,BI_ETIME,BI_TIMEUTILIZED,BI_OPENINGBAL,BI_CLBAL,

BI_BILLEDAMT,BI_USERIP,BI_SERVICENAME,BI_BYTESIN,BI_BYTESOUT,BI_BYTES,BI_REMARKS,BI_PUBLICIP,BI_SAMIP) values

(’122453106710.31.87.80′,’mdz123′,’Default’,'D4NL’,'2008-10-21 03:38:23′,

‘2008-10-21 06:10:24′,152,197.09,195.08,’2.01′,’10.31.87.80′,’F',295137740,125414454,420552194,’D',’118.9.4.47′,’210.1.80.3′)’
Skip_counter: 0
Exec_master_log_pos: 150587868
Relay_log_space: 157983746
1 row in set (0.00 sec)

mysql> set global sql_slave_skip_counter=1;start slave;show slave status\G
Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

*************************** 1. row ***************************
Master_Host: x.x.4.3
Master_User: replicate
Master_Port: 3307
Connect_retry: 60
Master_Log_File: master.077
Read_Master_Log_Pos: 7394212
Relay_Log_File: slave- relay-bin.010
Relay_Log_Pos: 150588010
Relay_Master_Log_File: master.076
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_do_db: bandnew,archive
Replicate_ignore_db:
Last_errno: 0
Last_error:
Skip_counter: 1
Exec_master_log_pos: 150587868
Relay_log_space: 157983746
1 row in set (0.00 sec)

Error: log file /mysql/data/mysqld/ib_logfile0 is of different size

ProblemStatement:

I have got the below error while starting the mysql after configuring a new slave with the tall ball of the master data directory.

081022 6:24:41 InnoDB: Warning: shutting down a not properly started
InnoDB: or created database!
081022 6:24:41 /usr/local/mysql4020/libexec/mysqld: Shutdown Complete

InnoDB: Error: log file /mysql/data/mysqld/ib_logfile0 is of different size 0 209715200 bytes
InnoDB: than specified in the .cnf file 0 104857600 bytes!
081022 6:24:42 Can’t init databases
081022 6:24:42 Aborting

Solution :

The same has been resolved by changing the below variable in the cnf file as same in the master config file

innodb_log_file_size = 200M

Error: ‘Access denied for user ‘replicate’@'10.0.0.8′ (using password: YES)’

Problem Statement:

we got the below error message while setting the replication.

Error: ‘Access denied for user ‘replicate’@'10.0.0.8′ (using password: YES)’.

Solution :

<18:09:58>root@6.83: ~#mysql -u root -p -h10.0.0.55 -P3306

If the error is password error then edit the password error.
Error: ‘Access denied for user ‘replicate’@'10.0.0.8′ (using password: YES)’

<18:09:58>root@6.83: ~#vi /etc/my.cnf (To change password, edit the cnf file)
<18:09:58>root@6.83: ~#less /data/mysqldata/err.log

mysql> change master to master_password=’xxxxx’;

mysql> change master to master_password=’replicate’,master_user=’replicate’,master_host=’10.0.0.55′,master_port=3306,master_log_file=’narnia-bin.000030′,master_log_pos=271266680;

mysql> stop slave;
mysql> start slave;

mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Connecting to master
Master_Host: 10.0.0.55
Master_User: replicate
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: arnia-bin.000030
Read_Master_Log_Pos: 271260976
Relay_Log_File: relay-bin.000004
Relay_Log_Pos: 4
Relay_Master_Log_File: arnia-bin.000030
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table: mail.appearance_new,pop.hostcnt
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 271266680
Relay_Log_Space: 4
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: NULL
1 row in set (0.00 sec)

Got fatal error 1236: ‘Client requested master to start replication from impossible position’ from master when reading data from binary log

Problem statement:

The below is problem I faced in a well running replication system.

Error Message :
081016 18:34:43 Error reading packet from server: Client requested master to start replication from impossible position (ser
ver_errno=1236)
081016 18:34:43 Got fatal error 1236: ‘Client requested master to start replication from impossible position’ from master when reading data from binary log
081016 18:34:43 Slave I/O thread exiting, read up to log ‘lot-bin.000065′, position 13664242
081016 18:35:04 Error reading relay log event: slave SQL thread was killed
081016 18:45:40 Slave SQL thread initialized, starting replication in log ‘lot-bin.000065′ at position 13664242, relay log’./mx5-relay-bin.000001′ position: 13664284
081016 18:45:40 Slave I/O thread: connected to master ‘replicate@10.0.4:3306′, replication started in log ‘lot-bin.
000065′ at position 13664242

Solution :
1) If the value of Read_Master_Log_Pos has a normal value, and slave asked weird position, this could be some internal bug. Now I see only a single way, but it could be difficult: if you have –log-slave-updates, use slave binary logs to find the last executed statement and it’s position in master logs, and CHANGE MASTER to that position.
2) Go onto the master execute
SHOW MASTER STATUS
Look at the output and find the log that the slave is pointing to. Look at the File size field.
Next look at the slave output from the slave reporting the issue. Look at Exec_Master_Log_Pos, is that value greater then the File Size on the master if so issue
CHANGE MASTER TO MASTER_LOG_FILE=[NEXT FILE], MASTER_LOG_POS=4;
slave start;

ERROR 1251: Client does not support authentication protocol

Problem Statement:

I got the below error while trying to accessing the upgraded mysqld server with a old client.

Error :

ERROR 1251: Client does not support authentication protocol
requested by server; consider upgrading MySQL client

Solution :

I have resolved the above my updating the password as below.

update user set password=old_password(’new_password’) where user=’user_name’ and host=’10.0.0.2′;

flush privileges;

and then try to access the mysqld server and now you will be able to connect to the server succesfully.