Solution

1. 1. Remove the symbolic link of privkey.pem under

      /etc/letsencrypt/live/[mydomain]/privkey.pem

   2. recreate the symbolic link with the dedicated user running Jupyter notebook.
   3. Run command as root:

      systemctl restart jupyterhub

Tricks

1. 1. • As the jupyter server is run by the ownership of a dedicated user, after the renewal, the private key, i.e. privkey.pem must be owned by this user. However, I run the command:

        certbot renew --standalone

        under root.

      • note that let’s encrypt command for CentOS 6 is quite different from CentOS7

Config

1. • OS: CentOS 7
   • Jupyter-notebook: 5.7.8

The post SSL Key Ownership appeared first on LarryLai.

Solution

• In the setting of the plugin, choose the tab Additional Firewall Rules
• Uncheck the option at the bottom, i.e. Advanced Character String Filter

Config

• WordPress 5.3
• All In One WP Security v4.4.2
• MathJax-LaTex v1.3.11

The post MathJax Load Failed – WP Security Plugin appeared first on LarryLai.

Background

After installing WP Health, it’s shown that both MariaDB 5 (a default replacement of MySQL for CentOS7) and PHP5.6 are obsolete, i.e. no more formal support and no security patches will be released. It’s suggested to upgrade at least to MariaDB10 and PHP7.

Apart from security and support concern, it’s known that PHP7 has better performance than PHP5.

Issue

After upgrading, either the Virtualmin has problem in displaying submenu on the left panel or there’re “Internal Server Error” on some WordPress sites. It’s found out that during yum update MariaDB, it’s required to remove the old MariaDB5, however, for packages dependency needs, yum will at the same time remove Postfix and Virtualmin-base. If these 2 packages are reinstalled after upgrading to MariaDB, then WordPress has problem.

Solution

Use rpm -e –nodeps to skip removal of Postfix and Virtualmin-base.

Tricks

After removal PHP5.6, list out all the related packages, e.g. php-mysqlnd, php-gd, etc. depending on my case, there’re some others. All these have to be reinstalled after installing PHP7.2 base package.

For upgrade of PHP7, never upgrade to the lastest PHP7.3 as some of the PHP packages do not have PHP7.3 compatible rpm, only have PHP7.2 compatible rpm. There’re many CentOS PHP7 upgrade info. on the web, but some are not good, after try and error, I use TecAdmin.net’s advice and got no problem.

Config

• CentOS: 7.6
• Virtualmin 6.06
• WordPress 5.1
• MariaDB: 10.1

The post Centos7 Virtualmin Upgrade PHP7 MariaDB appeared first on LarryLai.

During scanning stage of running the Duplicator plugin on a WordPress site, there was an error: Server Error 500.

Solution:

Modify /etc/php.ini file to increase memory:

memory_limit = 256M

from 128M

Tricks:

Even there is error during the scanning stage, Duplicator still allowed building step to proceed and showing no error.

Error 500 actually does not tell anything informative

No special message was logged in Apache web server

Config:

• PHP               5.6.30
• WordPress     4.7.4
• Duplicator     1.2.4

The post WordPress Duplicator Plugin Server Error 500 appeared first on LarryLai.

After installing WP Fastest Cache plugin, whenever update any plugin, there is error – Update failed. Could not remove old plugin.

Solution:

1. Go to WPFC at the top bar
2. Delete Cache and Minified CSS/JS
3. Update the plugin that needs to be updated

Tricks:

In case after installing WP Fastest Cache for quite a while, then there is need to update any other plugin and you found error. It is difficult for us to remember it should be the WPFC goes wrong.

The performance of this plugin for page access speed for my case is even better than other caching plugin like WP 3C Total Cache

Config:

• WordPress    4.7.3
• WP Fastest Cache     0.8.6.7

The post WP Fastest Cache Plugins Update Issue appeared first on LarryLai.

When moving some of the content to a single page design, the menu link will be addressing the div id instead of another page. But after all set up perfectly, the menu item link to the correct anchor, but missed to locate the correct position of the section, i.e. the anchor, div id.

Solution:

Using a WordPress plugin: Page Scroll to id and tuned the delay for scrolling setting

Tricks:

Better starts with a larger no. of delay and fine tune it to a smaller but large enough time delay for the page to run other scripts. In my case, heavy rendering for the Math symbol by MathJax may cause the missing position issue.

Config:

• WordPress     4.7.2
• Themify Theme Shoppe  1.0.2
• Page Scroll to id:  1.6.2

The post Scrolling to Section ID Missing appeared first on LarryLai.

error: “Sorry, no products matched your selection. Please choose a different combination.”
WooCommerce in WordPress shows all variations of variable product including unmatched variations thus the above error message may occur. But it used to be working fine. Perhaps, the error occurred after a WooCommerce update.

Solution:

Update php version from 5.4 to 5.6. Since php version 5.6 is not in the official repository of CentOS 7 as of Jan 2016, follow this thread on CentOS to install php56u works fine.

Tricks:

1. Click on System Status under WooCommerce plugin. There is a warning on php version under Server Environment stating that php 5.6 or above is required, … php5.4 is running.
2. As of Jan 2016, latest php version in the official repository of CentOS 7 is still the very old php5.4. Thus, 3rd party repository must be considered in order to install php5.6 on CentOS 7.
3. Some advise updating php with Webtatic’s php56w, but CentOS forum states that it is not recommended to use Webtatic repository.
4. After installing/ replacing php5.4 with php56u, some php extensions may not be compatible with the new version. And these extensions have to be updated too. E.g. Imagick has to be updated. If PECL is in place, the following command works fine:

#yum install php56u-pecl-imagick

Config:

• CentOS 7.3
• WordPress 4.7.1
• WooCommerce plugin   2.6.13

The post WooCommerce Showing Unmatched Variations appeared first on LarryLai.

It is quite terrifying if suddenly all the custom CSS disappear and you do not have a backup of the text of the custom CSS that is not just one or two lines, but it is filled with many lines.

Issue:

After updating theme Accelerate to the latest version as suggested by WordPress, all the custom CSS under Appearance admin menu of the child theme was gone.

Solution:

Restore to the original Virtual Machine hosting WordPress to the version just before updating the theme by Mac’s TimeMachine.

Tricks:

• It is supposed that the child theme would not be altered after updating the parent theme. However, I guess (as I’m not a WP framework expertise) that WordPress 4.7 removed the custom CSS option and instead deployed “Additional CSS” option, and put it in another area in the database rather than under the configuration of the theme.
• Before updating the theme version, there was no issue on the prior update of WordPress 4.6.1 to 4.7. But still the issue may not be caused by merely the latest theme version.
• Though TimeMachine can restore previous backup of Virtual Machine, it is more convenient to restore the snapshot of a Virtual Machine if there is a snapshot taking just before starting the theme update. In this case, how do people expect a child theme could be altered by updating the parent theme version?

Config:

• WordPress     4.7
• Theme            Accelerate 1.2.9
• Mac OS X      10.12.2

The post WordPress Custom CSS Disappear appeared first on LarryLai.

“Error: Missing argument to \begin” when using \color command and together with \boxed command in WordPress with MathJax plugin as if they are under LaTex syntax.

Solution:

Adding {} to embrace the content under the \color command. Actually, in LaTex syntax, \color command does not need to use {} as all content after the \color is coloured according to the defined color, e.g. \color{red}. However, for MathJax, you cannot add another LaTex command immediately after \color command, and you need to add {} to embrace the content to be coloured. For example, \color{red}{\boxed{f(x)}}

Config:

• WordPress:         2.6.1
• MathJax plugin:  1.3.4

The post MathJax Incompatibility to LaTex appeared first on LarryLai.

While conducting Online Live Class using Join.Me, and I need to select real-time video as profile. However, it seems that the built-in view camera in iMac cannot make any adjustment. So how can I make my profile more professional without adding an external camera?

Solution:

By using an application – iGlasses, it is easy to make adjustments to the setting of the built-in view camera

Tricks:

• iGlasses is compatible and integrating into all applications for the iMac is not a problem. It is as easy as selecting another view camera
• There is no free alternative for iGlasses on iMac, don’t waste time to find one!
• It is definitely worth the one-time charge. Moreover, A free trial period can give more confidence before buying it.
• In brief, this app leverages the capabilities of the built-in camera

Config:

• iMac          2014
• OS X         10.12.1
• iGlasses    v3.4.8

The post iMac View Camera Capability appeared first on LarryLai.