在Linux下面安裝mysql5.7版本，配置/etc/my.cnf檔案，按照安裝步驟到mysql/support-files目錄下，發現缺少這個my_default.cnf預設的配置檔案，如果沒有預設的配置檔案，需要在該目錄下面手動建立一個my_default.cnf配置檔案。

下面是網上通用的自定義my_default.cnf檔案內容：

# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html
# *** DO NOT EDIT THIS FILE. It's a template which will be copied to the
# *** default location during install, and will be replaced if you
# *** upgrade to a newer version of MySQL.


[mysqld]
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES 


# 一般配置選項
basedir = /usr/local/mysql
datadir = /usr/local/mysql/data
port = 3306
socket = /usr/local/mysql/mysqld/mysql.sock
character-set-server=utf8


#下面是可選項，要不要都行，如果出現啟動錯誤，則全部註釋掉，保留最基本的配置選項，然後嘗試新增某些配置項後啟動，檢測配置項是否有誤
back_log = 300
max_connections = 3000
max_connect_errors = 50
table_open_cache = 4096
max_allowed_packet = 32M
#binlog_cache_size = 4M


max_heap_table_size = 128M
read_rnd_buffer_size = 16M
sort_buffer_size = 16M
join_buffer_size = 16M
thread_cache_size = 16
query_cache_size = 128M
query_cache_limit = 4M
ft_min_word_len = 8


thread_stack = 512K
transaction_isolation = REPEATABLE-READ
tmp_table_size = 128M
#log-bin=mysql-bin
long_query_time = 6


server_id=1


innodb_buffer_pool_size = 1G
innodb_thread_concurrency = 16
innodb_log_buffer_size = 16M
innodb_log_file_size = 512M
innodb_log_files_in_group = 3
innodb_max_dirty_pages_pct = 90
innodb_lock_wait_timeout = 120
innodb_file_per_table = on


[mysqldump]
quick


max_allowed_packet = 32M


[mysql]
no-auto-rehash
default-character-set=utf8
safe-updates


[myisamchk]
key_buffer = 16M
sort_buffer_size = 16M
read_buffer = 8M
write_buffer = 8M


[mysqlhotcopy]
interactive-timeout


[mysqld_safe]
log-error=/usr/local/mysql/log/mysqld.log  
pid-file=/usr/local/mysql/mysqld/mysqld.pid  
open-files-limit = 8192

配置完畢，記得 cp   my_default.cnf    /etc/my.cnf

如果按照標準配置了mysql服務就可以  執行 service  mysqld  start    或者   /etc/init.d/mysqld start

服務正常啟動之後可以通過   ps  -ef|grp  mysql   查詢程序是否存在

連線myql服務    mysql -u root -p 

注意：如果報錯 Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) 

可以嘗試在  /etc/my.cnf 檔案中新增如下內容：

[client]
socket=/usr/local/mysql/mysqld/mysql.sock
[mysqld]
socket=/usr/local/mysql/mysqld/mysql.sock

另外，在安裝的過程中新建的mysql相關的檔案及資料夾，注意使用者、使用者組、許可權範圍，拒絕入坑！