Roberto's blog

30.09.22

WordPress development tricks

Expanding on Moving a WordPress instance by hand, here’s my list of hacks and tricks necessary for managing local WordPress instances.

Send PHP development server (‘wp server’) logs to a separate file

1. In php-cli’s php.ini (should be somewhere under /etc/php), set:
   log_errors = On
error_log = /var/log/php_errors.log
2. sudo chmod 777 /var/log/php_errors.log (yeah, whatever)

Catch emails

1. Install mailcatcher: gem install mailcatcher (requires rubygems package to be installed)
2. In php-cli’s php.ini, set sendmail_path = /usr/bin/env catchmail
3. At the very bottom of wp-config.php, below where it loads wp-settings.php, put:

if (defined('WP_CLI')) {
    WP_CLI::add_wp_hook('wp_mail_from', function () {
        return '[email protected]';
    });
} else {
    add_filter('wp_mail_from', function () {
        return '[email protected]';
    });
}

(otherwise WordPress will fail to send emails, saying “Invalid address: (From): wordpress@localhost”)

Use more workers for the PHP development server

This may make things faster, but it may also slow things down to a crawl. Give it a shot.

Simply append PHP_CLI_SERVER_WORKERS=N before the wp server command, like so:

PHP_CLI_SERVER_WORKERS=50 wp server

Kill and restart a hanging PHP development server

If you see pages infinitely loading, just CTRL-C the development server and kill all its workers before trying to restart it by doing:

pkill -f 8080      # <-- Replace '8080' with whatever port you used

Disable Dark Reader

Both in Firefox and Chrome, something in the browser plugin Dark Reader’s logic triggers multiple background loads of the index, which really slows things down when using PHP’s development server.

Fix uploads not working even though file permissions are OK

This could be caused by the upload_path setting in the wp_options table. To fix, clear the field:

UPDATE wp_options SET option_value = '' WHERE option_name = 'upload_path';

30.08.22

Recovering Dovecot mailboxes from disk (cPanel, Maildir format to Mbox)

I was given a backup of a hard drive containing cPanel-managed mailboxes and wanted to recover them into a readable format. When spinning up a new server using the drive backup, I could no longer access webmail or IMAP due to a cPanel license issue which I tried to work around but quickly disregarded. cPanel uses Dovecot to manage user mail.

What follows is a quick manual on how to recover and read Dovecot mailboxes given only disk access, a couple of scripts and a mail client that can read Mbox files.

We assume the mailboxes are stored in the Maildir++ format. These can be recognized by their directory structure: they always contain subdirectories cur, new, and usually tmp.

1. Find and copy the mailboxes

On my particular cPanel-managed server, the maildirs were located in /home/<user>/mail and there were also sub-maildirs in /home/<user>/mail/<domain>/<account>
Specific folders in the mailboxes used hidden directories like .Sent or .Trash.

You should be able to find maildirs by running:

find / -type d -name cur

Copy them all to a temporary workspace directory somewhere.

2. Unzip e-mails where necessary

I found that some of the e-mails were garbled when later converting the maildir to an mbox file.
This turned out to be because some (newer) mails were being stored gzipped.

I wrote a quick shell script to walk over all the e-mails and g-unzip them: maildir-gunzip.sh
Don’t use it on the originals, make a copy first!

To use:

chmod +x maildir-gunzip.sh # Make it executable
./maildir-gunzip.sh /path/to/copy-of-maildir

3. Convert to an Mbox file

Mbox files are a convenient, and perhaps the most common format for moving mailboxes around.
There is a nice script called maildir2mbox.py which has been adapted by various people over the years.
The most recent version I could find was one by Github user bluebird75. Download the script here. (mirror)

Make sure you have Python v3 installed on your machine.

Run the script like so:

maildir2mbox -r /path/to/maildir-copy outputfile.mbox

This Dovecot docs page contains an alternative script for this written in Perl, as well as some scripts for converting between other formats.

4. Open the Mbox file

Any email client that can read Mbox files will do.
I used Evolution. In Evolution, go to File > Import and follow the steps.
Make sure you make a new directory to import in so you can easily delete the emails later.

30.08.22

Extracting MySQL databases from a disk backup, the easy way

A lot of guides online tell you that, if you want to restore a MySQL instance using only a backup of the /var/lib/mysql directory, you should recover/rebuild the entire operating system that MySQL ran on.

It’s true that you should mimic the original setup, but only with regards to the MySQL version and sometimes whether MariaDB or MySQL were used. Once you’ve got that, you can very easily spin the database up again using Docker. Assuming you know the database user+password, you can just run mysqldump as you normally would.

Below are the steps that worked for me.

1. Determine MySQL version

Find the location of the mysql or mariadb binary:

find /thebackup -type f -name mysql -or -name mariadb

I had a rough idea of what the version would be so I ran strings and searched for 8.0:

$ strings /thebackup/usr/bin/mysql | grep '8\.0'
8.0.25
/build/mysql-8.0-eXpnQw/mysql-8.0-8.0.25/sql-common/client.cc
/build/mysql-8.0-eXpnQw/mysql-8.0-8.0.25/sql-common/client_plugin.cc
...

An alternative which may work generically:

strings /thebackup/usr/bin/mysql | grep '^/build'

2. Start the database in Docker

Now that we have the exact version number (8.0.25), we can spin up a Docker container for it:

docker run --rm --name mysql-recovery -v /thebackup/var/lib/mysql:/var/lib/mysql mysql:8.0.25 --skip-grant-tables --user=mysql

Replace mysql:<version> with mariadb:<version> if it’s MariaDB.

Note that we’re mounting the mysql lib directory into the container using -v. If you want to play it safe, make an extra backup of /var/lib/mysql first.

3. Extract data

You can now browse or dump the data using command-line tools:

docker exec -it mysql-recovery mysql
docker exec mysql-recovery mysqldump mydatabase > mydatabase-backup.sql

15.02.22

Moving a WordPress instance by hand

Over the years I’ve migrated a lot of WordPress sites. Although there are plugins that can take care of it, I have yet to find a more efficient way than just doing it by hand. The following is my recipe for migrating WordPress instances.

In the example we move a site to our local development environment.

Prerequisites

• Shell (usually SSH) access to the server that runs the WordPress instance
• PHP CLI (sudo apt install php-cli)
• WP-CLI

Exporting the database

The quickest way is to use wp-cli:

cd public_html
wp db dump example.com.sql

If that doesn’t work, here’s the manual way:

cd public_html
# Find database credentials
grep DB_ wp-config.php
# Create a database dump
mysqldump somedb -u someuser -p'somepassword' > example.com.sql

Archiving the website

Make a tarball of the site’s files:

tar czf example.com.tgz public_html

If it’s only for testing and you’re in a hurry, exclude the WP Uploads directory:

tar czf example.com.tgz --exclude=**/wp-content/uploads/* public_html

Now copy the tarball over to your machine.

Setting up local environment

1. Unpack the WordPress instance:
   tar xzf example.com.tgz
2. Update database credentials in wp-config.php
   For local development, I usually just take user ‘root’ with an empty password (the Gods of Security frown upon me)
3. Create and import the database, e.g.:
   sudo mysqladmin create example_com
cd public_html
wp db cli < example.com.sql
4. To not need HTTPS locally:
   a. Remove any line containing “FORCE_SSL_ADMIN” from wp-config.php
   b. Remove or rename (= deactivate) any plugin (from wp-content/plugins) that forces ssl, for instance ‘really-simple-ssl’
5. Replace your WordPress base URL using wp-cli:
   wp search-replace https://example.com http://localhost:8080
6. Run the local development server:
   wp server --port=8080

You should now be able to access the WordPress site by visiting http://localhost:8080 !

Optional, but handy

Create an admin user for yourself:
wp user create myadmin [email protected] --role=administrator --user_pass=admin

Troubleshooting

If connecting to the database fails, it could be that an empty password is not accepted. As using root with an empty password is a bit of a hack, here’s another hack to make it work for newer versions of MySQL/MariaDB. Obtain a root MySQL shell and execute:

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '';
FLUSH PRIVILEGES;

Further (necessary) tweaking

See WordPress development tricks

30.08.20

Moving commits to a rewritten git repository

The situation: a git repository had been fully prettify-ed using git filter-branch, but I kept working in a separate branch of the old version of the repository.

It seems that git filter-branch could not help me, as the new repository’s internal structure was no longer compatible with my old branch. Therefore, I used this quick and dirty shell script. It worked!

#!/bin/bash
#######################################
# Before running:
#   1. Replace 'oldproject', 'newproject' and the contents of STARTCOMMIT
#   2. Put this script in a directory above oldproject and newproject
#   3. chmod +x thisscript.sh
#
# Use at your own risk.
#######################################

cd oldproject

STARTCOMMIT="...";
COMMITS="$(git log --oneline $STARTCOMMIT..HEAD  | tac | awk '{print $1}')"

for COMMIT in $COMMITS; do
  echo "******************** $COMMIT *****************"
  MESG="$(git log --pretty=format:'%s' $COMMIT~1..$COMMIT)"
  FILES="$(git diff-tree --no-commit-id --name-only -r $COMMIT | grep -v package-lock)"

  # Copy files within commit
  for FILE in $FILES; do
    git show $COMMIT:$FILE > ../newproject/$FILE
  done

  cd ../newproject/

  # Run 'prettier' on the files
  # NOTE: this can be optimized by only using files from $FILES
  node_modules/.bin/prettier --no-config --single-quote --tab-width=4 \
  --arrow-parens always --use-tabs --print-width=140 --write "**/**.js"
  git add -A
  git commit -m "$MESG"

  cd ../oldproject
done

31.01.20

Ubuntu MATE freezes right after showing desktop

Today, my Ubuntu MATE 19.04 desktop froze and stalled the system, right after showing the main desktop and while populating the main panel’s system tray; screen went black, keyboard lighting jumped on and keyboard commands would no longer have effect. Switching terminals with CTRL-ALT-F* had no effect. Kernel panic?

Booting to recovery mode however did work. Tried some things to no avail:

• Blacklisting the wifi driver (ath10k_pci)
• Switching graphics card from Nvidia to Intel
• systemctl disable bluetooth
• systemctl disable NetworkManager
• Backing up and removing ~/.config/autostart
• Backing up and removing ~/.config/mate-session

No suspicious warnings to be seen in /var/log/syslog*, /var/log/dmesg*, /var/log/Xorg.0.log* or anything else, so likely not a hardware issue.

The problem turned out to be a corrupted directory somewhere under ~/.config. The fix was simply to restore a backup of the .config directory.

Suspected culprits:

• ~/.config/gtk-2.0
• ~/.config/mate
• ~/.config/my-weather-indicator

14.11.18

Retrieving git submodules without a .git directory

This comes in handy when you have a copy of a git repository without the .git metadata directory included, for instance a .zip export from Bitbucket.

For use in a shell script.

if [ ! -d '.git' ]; then
    git init .

    # Reconstruct submodules using .gitmodules
    # Based on https://stackoverflow.com/a/11258810
    git config -f .gitmodules --get-regexp '^submodule\..*\.path
 
    while read path_key path
    do
        rm -rf $path
        url_key=$(echo $path_key | sed 's/\.path/.url/')
        branch_key=$(echo $path_key | sed 's/\.path/.branch/')
        url=$(git config -f .gitmodules --get "$url_key")
        branch=$(git config -f .gitmodules --get "$branch_key")
        git submodule add -b $branch --depth 1 $url $path
    done
fi

# Continue as we would /with/ a .git directory
git submodule foreach --recursive 'git fetch --tags'
git submodule update --recursive --init

7.09.16

Drupal 8 in a subdirectory with nginx

Assuming this nginx configuration as a starting point:

root /var/www/example.org/web;

location / {
  try_files $uri @rewrite;
}

location @rewrite {
  rewrite ^ /index.php;
}

You can configure your Drupal 8 instance to run in a subdirectory of the site with two simple steps.

In this example we change the instance’s base url from http://example.org/ to http://example.org/subdir/.

1. Change nginx configuration

Replace the ‘location /’ block with this:

location ~ /subdir/(.*) {
  try_files /$1 @rewrite;
}

2. Change Drupal settings.php

Add the following to your settings.php (or settings.X.php):

if(isset($GLOBALS['request'])) {
  $scriptName = $GLOBALS['request']->server->get('SCRIPT_NAME');
  $scriptName = preg_match('#^/subdir/#', $scriptName) ? : "/subdir$scriptName";
  $GLOBALS['request']->server->set('SCRIPT_NAME', $scriptName);
}

… and that’s it!

Hopefully there will be a cleaner way of doing this in the future…

Tested with Drupal 8.1.6.

16.11.14

Nginx custom autoindex without FancyIndex

Sending your friends an open directory in your site isn’t fun unless it has random ASCII art under it. :-)

Nginx lets one customise the look of open directories using the FancyIndex module. Unfortunately Debian Wheezy doesn’t include this module, unless you get nginx-extras from the wheezy-backports repository. As an alternative, I chose to hack up something in PHP for a similar effect.

Read the rest of this entry »

13.07.14

Recursive FLAC to MP3 converter

I like my music to be in MP3 v0, meaning the data has a variable bitrate of between 200-300 kbit/s. It makes for tiny MP3s that are in my opinion almost indistinguishable from ‘pure’ CD quality, sound-wise.

However, to get music in that format is not always possible, so my music directory has become littered with FLACs. Converting them all to v0 the simple way means the poor old NAS will have a hard time keeping up with other tasks. Enter flac2mp3.sh:

Read the rest of this entry »

Recent Posts

• WordPress development tricks
• Recovering Dovecot mailboxes from disk (cPanel, Maildir format to Mbox)
• Extracting MySQL databases from a disk backup, the easy way
• Moving a WordPress instance by hand
• Moving commits to a rewritten git repository

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