[root@gettestlnx02 ~]# mysql --help | grep my.cnf

                      order of preference, my.cnf, $MYSQL_TCP_PORT,

/etc/my.cnf /etc/mysql/my.cnf /usr/etc/my.cnf ~/.my.cnf 

[root@gettestlnx02 ~]# ls /etc/my.cnf /etc/mysql/my.cnf /usr/etc/my.cnf ~/.my.cnf

ls: cannot access /etc/mysql/my.cnf: No such file or directory

ls: cannot access /usr/etc/my.cnf: No such file or directory

ls: cannot access /root/.my.cnf: No such file or directory

/etc/my.cnf

[root@gettestlnx02 ~]# 

mysql> show variables like '%log_error%';

+---------------------+---------------------+

| Variable_name       | Value               |

+---------------------+---------------------+

| binlog_error_action | ABORT_SERVER        |

| log_error           | /var/log/mysqld.log |

| log_error_verbosity | 3                   |

+---------------------+---------------------+

3 rows in set (0.00 sec)

mysql> exit

Bye

[root@gettestlnx02 ~]# mv /etc/my.cnf  /tmp/my.cnf

[root@gettestlnx02 ~]# ls -lrt /etc/my.cnf

ls: cannot access /etc/my.cnf: No such file or directory

[root@gettestlnx02 ~]# service mysqld stop

Stopping mysqld:  [  OK  ]

[root@gettestlnx02 ~]# service mysqld start

Starting mysqld:  [  OK  ]

[root@gettestlnx02 ~]# 

# Extract value of a MySQL option from config files

# Usage: get_mysql_option OPTION DEFAULT SECTION1 SECTION2 SECTIONN

# Result is returned in $result

# We use my_print_defaults which prints all options from multiple files,

# with the more specific ones later; hence take the last match.

get_mysql_option () {

    option=$1

    default=$2

    shift 2  #移动到第3个参数，详情见下面调试。

    result=$(/usr/bin/my_print_defaults "$@" | sed -n "s/^--${option}=//p" | tail -n 1)

    if [ -z "$result" ]; then

        # not found, use default

        result="${default}"

    fi

}

get_mysql_option datadir "/var/lib/mysql" mysqld

datadir="$result"

get_mysql_option socket "$datadir/mysql.sock" mysqld

socketfile="$result"

get_mysql_option log-error "/var/log/mysqld.log" mysqld mysqld_safe

errlogfile="$result"

get_mysql_option pid-file "/var/run/mysqld/mysqld.pid" mysqld mysqld_safe

mypidfile="$result"

[root@gettestlnx02 ~]# file /usr/bin/my_print_defaults

/usr/bin/my_print_defaults: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, not stripped

[root@gettestlnx02 ~]# /usr/bin/my_print_defaults mysqld

[root@gettestlnx02 ~]# 

[root@gettestlnx02 ~]# ls /tmp/my.cnf

/tmp/my.cnf

[root@gettestlnx02 ~]# /usr/bin/my_print_defaults mysqld

[root@gettestlnx02 ~]# mv /tmp/my.cnf  /etc/my.cnf

[root@gettestlnx02 ~]# /usr/bin/my_print_defaults mysqld

--datadir=/var/lib/mysql

--socket=/var/lib/mysql/mysql.sock

--symbolic-links=0

--log-error=/var/log/mysqld.log

--pid-file=/var/run/mysqld/mysqld.pid

[root@gettestlnx02 ~]# service mysqld stop

Stopping mysqld:  [  OK  ]

[root@gettestlnx02 ~]# mv /etc/my.cnf  /tmp/my.cnf

[root@gettestlnx02 ~]# service mysqld start

Initializing MySQL database:  2018-03-16T01:26:19.589182Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).

2018-03-16T01:26:20.034494Z 0 [Warning] InnoDB: New log files created, LSN=45790

2018-03-16T01:26:20.132219Z 0 [Warning] InnoDB: Creating foreign key constraint system tables.

2018-03-16T01:26:20.193504Z 0 [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: 07ee8c42-28b9-11e8-a04a-005056b3ebdf.

2018-03-16T01:26:20.208662Z 0 [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened.

2018-03-16T01:26:20.209919Z 1 [Note] A temporary password is generated for root@localhost: O;kZmIj+.6jf

[  OK  ]

Logging to '/var/lib/mysql/gettestlnx02.err'.

Starting mysqld:  [  OK  ]

[root@gettestlnx02 mysql]# cd /var/lib/mysql

[root@gettestlnx02 mysql]# ls -lrt

total 122948

-rw-r-----. 1 mysql mysql 50331648 Mar 16 09:26 ib_logfile1

-rw-r-----. 1 mysql mysql       56 Mar 16 09:26 auto.cnf

drwxr-x---. 2 mysql mysql     4096 Mar 16 09:26 performance_schema

drwxr-x---. 2 mysql mysql     4096 Mar 16 09:26 mysql

drwxr-x---. 2 mysql mysql    12288 Mar 16 09:26 sys

-rw-r-----. 1 mysql mysql      420 Mar 16 09:26 ib_buffer_pool

-rw-------. 1 mysql mysql     1679 Mar 16 09:26 ca-key.pem

-rw-r--r--. 1 mysql mysql     1107 Mar 16 09:26 ca.pem

-rw-------. 1 mysql mysql     1675 Mar 16 09:26 server-key.pem

-rw-r--r--. 1 mysql mysql     1107 Mar 16 09:26 server-cert.pem

-rw-------. 1 mysql mysql     1675 Mar 16 09:26 client-key.pem

-rw-r--r--. 1 mysql mysql     1107 Mar 16 09:26 client-cert.pem

-rw-------. 1 mysql mysql     1675 Mar 16 09:26 private_key.pem

-rw-r--r--. 1 mysql mysql      451 Mar 16 09:26 public_key.pem

-rw-------. 1 mysql mysql        6 Mar 16 09:26 mysql.sock.lock

srwxrwxrwx. 1 mysql mysql        0 Mar 16 09:26 mysql.sock

-rw-r-----. 1 mysql mysql 12582912 Mar 16 09:26 ibtmp1

-rw-r-----. 1 mysql mysql 12582912 Mar 16 09:26 ibdata1

-rw-r-----. 1 mysql mysql 50331648 Mar 16 09:26 ib_logfile0

-rw-r-----. 1 mysql mysql     3277 Mar 16 09:27 gettestlnx02.err

[root@gettestlnx02 mysql]# 

start(){

    [ -x $exec ] || exit 5

    # check to see if it's already running

    RESPONSE=$(/usr/bin/mysqladmin --no-defaults --socket="$adminsocket" --user=UNKNOWN_MYSQL_USER ping 2>&1)

    if [ $? = 0 ]; then

        # already running, do nothing

        action $"Starting $prog: " /bin/true

        ret=0

    elif echo "$RESPONSE" | grep -q "Access denied for user"

    then

        # already running, do nothing

        action $"Starting $prog: " /bin/true

        ret=0

    else

        # prepare for start

        if [ ! -e "$errlogfile" -a ! -h "$errlogfile" -a "x$(dirname "$errlogfile")" = "x/var/log" ]; then

            install /dev/null -m0640 -omysql -gmysql "$errlogfile"

        fi

        [ -x /sbin/restorecon ] && /sbin/restorecon "$errlogfile"

        if [ ! -d "$datadir/mysql" ] ; then

            # First, make sure $datadir is there with correct permissions

            if [ ! -d "$datadir" -a ! -h "$datadir" -a "x$(dirname "$datadir")" = "x/var/lib" ]; then

                install -d -m0751 -omysql -gmysql "$datadir" || exit 1

            fi

            if [ ! -h "$datadir" -a "x$(dirname "$datadir")" = "x/var/lib" ]; then

                chown mysql:mysql "$datadir"

                chmod 0751 "$datadir"

            fi

            if [ -x /sbin/restorecon ]; then

                /sbin/restorecon "$datadir"

                for dir in /var/lib/mysql-files /var/lib/mysql-keyring ; do

                    if [ -x /usr/sbin/semanage -a -d /var/lib/mysql -a -d $dir ] ; then

                        /usr/sbin/semanage fcontext -a -e /var/lib/mysql $dir >/dev/null 2>&1

                        /sbin/restorecon -r $dir

                    fi

                done

            fi

            # Now create the database

            initfile="$(install_validate_password_sql_file)"

            action $"Initializing MySQL database: " /usr/sbin/mysqld --initialize --datadir="$datadir" --user=mysql --init-file="$initfile"

            ret=$?

            rm -f "$initfile"

            [ $ret -ne 0 ] && return $ret

            # Generate certs if needed

            if [ -x /usr/bin/mysql_ssl_rsa_setup -a ! -e "${datadir}/server-key.pem" ] ; then

                /usr/bin/mysql_ssl_rsa_setup --datadir="$datadir" --uid=mysql >/dev/null 2>&1

            fi