Christopher Juckins

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centos_7_migration_notes [2021/05/03 12:51] – juckinscentos_7_migration_notes [2023/12/14 10:10] – juckins
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 RHEL5/6/7 Cheatsheet: {{:rhel_5_6_7_cheatsheet_201410.pdf|}} RHEL5/6/7 Cheatsheet: {{:rhel_5_6_7_cheatsheet_201410.pdf|}}
 +
 +[[https://tuxcare.com/extended-lifecycle-support/ Tuxcare's CentOS 7 Extended Support]]
 +
 +
 +14 Dec 2023 (for Dell XPS 8930 tower):
 +  * Updated kernel from kernel-3.10.0-1160.102.1.el7.x86_64 to kernel-3.10.0-1160.105.1.el7.x86_64
 +  * Attempted to rebooted machine but after the BIOS splash screen, only got a blank screen with blinking cursor in upper-left corner 
 +  * Restarted machine using the power button but had same condition
 +  * Restarted once again but at the BIOS splash screen selected F12
 +  * For boot options, chose Boot from Hard Drive and list of kernels appeared
 +  * Chose latest kernel and machine was OK
 +  * After machine was running, did another restart and machine powered up with no issues
 +
 +23 Oct 2023 (for Dell XPS 8930 tower)
 +  * Updated kernel from kernel-3.10.0-1160.99.1.el7.x86_64 to kernel-3.10.0-1160.102.1.el7.x86_64 and then machine would not boot, just blank screen with blinking cursor in upper-left corner
 +  * Powered off machine, unplugged the USB peripheral cables
 +  * Unplugged power cable for 30 seconds
 +  * Rebooted and used F12 to go into BIOS Boot Options
 +  * Tried to boot to Hard Drive but that immediately failed with error 'press any key to reboot'
 +  * After that, the machine booted up OK and the normal selection of kernels appeared
  
 Other fixes: Other fixes:
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       * ''pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on '127.0.0.1' ([Errno 99] Cannot assign requested address)")''       * ''pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on '127.0.0.1' ([Errno 99] Cannot assign requested address)")''
   * Updated /etc/my.cnf.d/server.cnf with this setting under [mariadb-5.5]   * Updated /etc/my.cnf.d/server.cnf with this setting under [mariadb-5.5]
-      * ''max_connections = 800'' + 
-  * ''systemctl restart mariadb.service'' +  max_connections = 818 (Note that 818 seems to be the absolute limit) 
-  * Other commands to check status of mariadb server: +  back_log = 1024 (Note that OS limit is in /proc/sys/net/ipv4/tcp_max_syn_backlog) 
-      * ''set global max_connections = 800;''+  thread_cache_size = 818 
 +  thread_handling = pool-of-threads 
 +   
 +Then do: ''systemctl restart mariadb.service'' 
 + 
 +  * Other commands to check and modify on mariadb server:
       * ''show variables like "max_connections";''       * ''show variables like "max_connections";''
-      * ''show global status like "Threads_connected"''+      * ''show global status like "Threads_connected";'' 
 +      * ''show status like "Conn%";'' 
 +      * ''show status like "Threads%";'' 
 +      * ''show global status;'' 
 +  * See https://mariadb.com/kb/en/configuring-mariadb-for-optimal-performance/
   * Also check python3 coding best practices for opening/closing database connections   * Also check python3 coding best practices for opening/closing database connections
 +    * I have noted that opening and closing the database connection only once in the python script helps reduce database "cannot assign requested address" errors
   * [[https://pypi.org/project/mysqlclient/|mysqlclient]] is supposedly [[https://stackoverflow.com/questions/43102442/whats-the-difference-between-mysqldb-mysqlclient-and-mysql-connector-python|faster than alternatives]]   * [[https://pypi.org/project/mysqlclient/|mysqlclient]] is supposedly [[https://stackoverflow.com/questions/43102442/whats-the-difference-between-mysqldb-mysqlclient-and-mysql-connector-python|faster than alternatives]]
       * import MySQLdb       * import MySQLdb
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   * Working crontabs for each user   * Working crontabs for each user
   * [[python_notes|Install Python 3]]   * [[python_notes|Install Python 3]]
 +
 +Optional:
 +  * [[https://gorilla.dp100.com/downloads/|Password Gorilla]] (use standalone executable)
  
 Contents of /etc/yum.repos.d (CentOS 7): Contents of /etc/yum.repos.d (CentOS 7):
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     * Yet another option is to use modules that are in a repository     * Yet another option is to use modules that are in a repository
  
-[[http://www.if-not-true-then-false.com/2010/install-adobe-flash-player-10-on-fedora-centos-red-hat-rhel/|Ensure Adobe Flash plugin is installed]]+<del>[[http://www.if-not-true-then-false.com/2010/install-adobe-flash-player-10-on-fedora-centos-red-hat-rhel/|Ensure Adobe Flash plugin is installed]]</del>
  
 [[http://www.cyberciti.biz/faq/howto-install-linux-apache-mariadb-php-lamp-stack-on-centos7-rhel7/|Ensure Apache is installed and running]] [[http://www.cyberciti.biz/faq/howto-install-linux-apache-mariadb-php-lamp-stack-on-centos7-rhel7/|Ensure Apache is installed and running]]
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   * [[http://howtolamp.com/lamp/httpd/2.4/customizing/|Tips for users and permissions #2]]   * [[http://howtolamp.com/lamp/httpd/2.4/customizing/|Tips for users and permissions #2]]
  
-[[centos_php7.2_upgrade|Upgrade PHP to version 7.2]]+<del>[[centos_php7.2_upgrade|Upgrade PHP to version 7.2]]</del> 
 + 
 +[[https://computingforgeeks.com/how-to-install-php-7-4-on-centos-7/|Upgrade PHP to version 7.4]]
  
 Migrate /etc/php.ini from old server and relax settings due to test env: Migrate /etc/php.ini from old server and relax settings due to test env:
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 Database work: Database work:
 +  * Update /etc/my.cnf.d/server.cnf with this setting under [mariadb-5.5]
 +    * ''max_connections = 800''
 +    * ''systemctl restart mariadb.service''
   * Backup /etc/my.cnf   * Backup /etc/my.cnf
     * Add this line under [mysqld]     * Add this line under [mysqld]
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       * systemctl start mariadb.service       * systemctl start mariadb.service
       * systemctl enable mariadb.service       * systemctl enable mariadb.service
-    * mysql DATABASE -h localhost -u USER -p'PASS' < /tmp/DATABASE.sql+    * mysql -u USER -p'PASSWORD' (to login to mysql at command line) 
 +      * CREATE DATABASE database_name; 
 +      * Now logout of command line 
 +    * mysql DATABASE_NAME -h localhost -u USER -p'PASS' < /tmp/DATABASE.sql
  
   * Note CentOS7 comes with PHP 5.4 and latest version of phpMyAdmin that will work is 4.4.x   * Note CentOS7 comes with PHP 5.4 and latest version of phpMyAdmin that will work is 4.4.x
centos_7_migration_notes.txt · Last modified: 2023/12/14 10:10 by juckins