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--- centos_7_migration_notes [2022/05/18 09:29] – juckins
+++ centos_7_migration_notes [2025/03/20 19:58] (current) – ↷ Links adapted because of a move operation juckins
@@ Line 2: / Line 2: @@
 RHEL5/6/7 Cheatsheet: {{:rhel_5_6_7_cheatsheet_201410.pdf|}}
+[[https://tuxcare.com/extended-lifecycle-support/|Tuxcare's CentOS 7 Extended Support]]
+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
+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:
@@ Line 13: / Line 33: @@
       * ''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]
-      * ''max_connections = 800''
-      * Note that 800 worked, but 818 seems to be the absolute limit
+  max_connections = 818 (Note that 818 seems to be the absolute limit)
-  * ''systemctl restart mariadb.service''
+  back_log = 1024 (Note that OS limit is in /proc/sys/net/ipv4/tcp_max_syn_backlog)
+  thread_cache_size = 818
+  thread_handling = pool-of-threads
+Then do: ''systemctl restart mariadb.service''
   * Other commands to check and modify on mariadb server:
-      * ''set global max_connections = 800;''
-        * Do that command inside phpMyAdmin logged in as root
       * ''show variables like "max_connections";''
       * ''show global status like "Threads_connected";''
@@ Line 24: / Line 47: @@
       * ''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
+    * 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]]
       * import MySQLdb
@@ Line 410: / Line 435: @@
   * [[Yum installer bash script (CentOS7)|Copy this source to a .bash and run as root]]
-[[install_configure_cpan|CPAN packages]] to install:
+[[perl_install_configure_cpan|CPAN packages]] to install:
   * <color #ed1c24>NOTE</color>: Do not update .bashrc for library locations or else they will go into the wrong path
     * [[http://stackoverflow.com/questions/33636231/installed-cpan-modules-in-problematic-location|Wrong location of perl libraries]]