Ubuntu 14.04.5LTS to 16.04.5LTS

Ubuntu 14.04.5LTS is a widely popular Linux distro for server and it still receives updates as of Feb 2019. However, the official maintenance period will soon end (April 2019) and hence it is prime time for upgrade.

Upgrading a standard LAMP from 14.04LTS to 16.04LTS is not as straight forward as it seems, especially the original server may be running for years receiving various patches to different minor versions (14.04.1, .2, .3, .4, and .5)

Below are the steps that had worked for me.

1. Ensure the 14.04 version is updated to 14.04.5LTS. This is the latest as of this writing. If you are running ISPConfig 3.1, it is recommended that you also upgrade ISPConfig prior to the distro upgrade.

2. apt-get update

3. apt-get upgrade

4. apt-get dist-upgrade

The above steps should patch the 14.04 to the latest version and with all the patches installed.

5. do-release-upgrade

This should then prompt a new version is ready for upgrade.

6. I have chosen to keep all existing "local" version of config files during the interactive upgrade process (which took about 50-60 minutes), depending on the speed of your server and internet connection etc. I am running on a Rackspace Cloud instance so the speed is quite fast.

7. A problem would occur at the end of the upgrade

(a) MySQL 5.5 to 5.7 upgrade did not work
(b) nano did not work (the binary can't be found)

7a - This is because MySQL 5.5 to 5.7 is not an official upgrade path. It should first be upgraded to 5.6 and then 5.7. Some internet articles suggest upgrading to MySQL 5.7 when you are still at 14.04LTS. I eventually solved this issue by following the steps here:

https://askubuntu.com/questions/760724/16-04-upgrade-broke-mysql-server

The steps are quoted below.

These are the steps I took to correct this:

1. Back up your my.cnf file in /etc/mysql and remove or rename it

   sudo mv /etc/mysql/my.cnf /etc/mysql/my.cnf.bak
   

2. Remove the folder /etc/mysql/mysql.conf.d/ using

   sudo rm -r /etc/mysql/mysql.conf.d/
   

3. Verify you don't have a my.cnf file stashed somewhere else (I did in my home dir!) or in /etc/alternatives/my.cnf use

   sudo find / -name my.cnf
   

4. Backup and remove /etc/mysql/debian.cnf files (not sure if needed, but just in case)

   sudo mv /etc/mysql/debian.cnf /etc/mysql/debian.cnf.bak
   sudo apt purge mysql-server mysql-server-5.7 mysql-server-core-5.7
   sudo apt install mysql-server
   

5. In case your syslog shows an error like "mysqld: Can't read dir of '/etc/mysql/conf.d/'" create a symbolic link:

   sudo ln -s /etc/mysql/mysql.conf.d /etc/mysql/conf.d
   

   Then the service should be able to start with sudo service mysql start.

That got it working!

Note on step 3, if you found the my.cnf (which I had 2 additional my.cnf, just delete them with rm command). There had been no need to start mysql at end of step 5 because the installation script had started it automatically.

7b) This can be resolved with a single command at shell

hash -r

8. apt-get autoremove - this should clean up the server and remove quite a number of old kernels

9. Re-configure Apache2 so that it runs in correct mode. Follow the articles here:
https://www.mobibrw.com/2017/7068

1	$ sudo service apache2 start

注意，此时Apache默认被切换到了Prefork MPM工作模式，我们需要手工切换回到Event MPM工作模式。

正常情况下，这个版本的Apache可能默认启用了内嵌的PHP 7.0支持，可是这些默认的模块是不能在Event MPM模块下工作的，切换后启动时候会报告如下错误：

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$ cat /var/log/syslog | grep Apache   May 22 10:46:12 apache2[25403]: [Mon May 22 10:46:12.731909 2017] [:crit] [pid 25414:tid 139656381421440] Apache is running a threaded MPM, but your PHP Module is not compiled to be threadsafe.  You need to recompile PHP.

由于我们使用Proxy的方式来调用，因此，我们实际上是不需要Apache内置PHP解析模块的，那么我们需要卸载这些模块：

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$ sudo apt-get remove libapache2-mod-php7.0   $ sudo apt-get remove libapache2-mod-php

这个版本（Apache 2.4.18）已经默认内置Event MPM了，因此，我们只需要简单的启用这个模块即可：

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$ sudo a2dismod mpm_prefork   $ sudo a2enmod mpm_event   $ sudo service apache2 restart

切换完成后执行

1	$ a2query -M

即可查询到当前启用的模型了。