David's Blog

One problem is that I need to install WP-CLI on the new server, and dealing with it is not easy.

The installation instructions don’t say one way or another, but WP-CLI should not be installed as root. Later, if you go to run it as root, it will bark at you that you’re doing a bad thing. Okay, nice to know.

But we do now have the problem that the user who runs WordPress (well, Apache, which runs the PHP code that is WordPress) is the www-data user. I cannot log in as the www-data user, by design (it is a good design). So, how to run this WP-CLI stuff?

sudo -u www-data wp <command>

Okay, this says to switch to user www-data (sudo = switch user and do) (the -u option specifies which user, in this case www-data), and run the wp binary and any command line options you want it (wp) to do.

Cool, but the user I’m logged in as has no idea of where the WordPress installation is. So now, every freaking command I have to type, sudo -u www-data wp <command>, also needs --path=/var/www/html/wordpress in there too.

This sucks.

There is supposed to be a file, wp-cli.local.yml, that I can put the path into. But that file is in my directory, and the sudo command switches away from that.

This sucks, still.

The www-data user does have a home directory; but, it won’t ever be used because the account runs /usr/sbin/nologin on every access. That is secure, but it doesn’t help me from having to type sudo -u www-data wp --path=/var/www/html/wordpress<command> every freaking time I need to do something.

Also, I am a fan of using the page-up key to search my bash history. That works great when I type a few letters, say gre and hit PgUp to search through my last few grep commands. Do I need to reassign ownership of files I’ve added to /var/www/html/wordpress/ ? chow and PgUp, and in a keystroke or two, I’ve got chown -R www-data:www-data /var/www/html/wordpress/ ready to run. Ditto the Apache2 enable and disable site commands. There are a ton of examples where just a few keystrokes and the PgUp key are great.

But having to type su and hitting PgUp presents me with a wall of noise, to finally find the command at the end that I actually want to repeat.

This sucks.

So, there is a solution. It seems kludgy, but it works, as long as you are willing to put up with its kludginess.

1. cd to /var/www/html/wordpress/
2. create a file, wp-cli.local.yml, in the location where WordPress is installed (where you just did the cd to), and inside it, put:
   • path: /var/www/html/wordpress

So, as long as you are already in the “right” place, and you have this file which points to your “right place”, you don’t have to specify the “right place” on the command-line of WP-CLI.

The other option is to be in my home directory, and do everything via bash scripts. I wanted to use the command-line, but I may need to put one more level of indirection in the process to get things to work easily. Like I said: kludge.

However, since the bash script has WPPATH="/var/www/html/wordpress" in it, all that sudo -u www-data nonsense goes away. Sure, I’m running it as some random user from some random location, but (I assume) that the WP-CLI people are just fine with that because if a random hacker gets into an ssh session on my box, I’m done for, anyway. Why not just assume whoever is running these commands is authorized?

This sucks quite a bit less, although it doesn’t make me warm and fuzzy about security.

I have a production WordPress site on Amazon Lightsail that I need to migrate away from. These are notes on how to migrate over only the stuff I want to keep.

Backstory: Amazon Lightsail was very inexpensive, at under $5 per month for hosting on their smallest machine, and it did fine. Two things became problems, however:

• Bitnami WordPress is super easy to spin up, and everything just works. But upgrading to a newer version of something (say PHP or MySQL or something) is a non-starter. The only way to upgrade is to spin up a new machine and do a migration to a new machine.
• Amazon recently did a price increase. Now, I can get a Linode machine with double the RAM for only $2 more, and that will include backups.

Okay, so I need to migrate, but over the years, I’ve tried different plugins, and even though many of them were uninstalled, the installation routine left crap in the database. How to migrate to a new server, but leave behind the crap? This will be the topic of this post.

First, I installed WP-CLI, instructions can be found here.

Then, on the new machine, I installed only those Plugins which I know I need.

I took a snapshot backup at this point, simply because it seems prudent.

On the new machine, I logged in with ssh and ran this:

wp --path='/var/www/html/wordpress' db query "SHOW TABLES" --skip-column-names --allow-root

This gives me a list of the tables in the new machine that I want from the old machine.

+-----------------------+
| wp_commentmeta        |
| wp_comments           |
| wp_links              |
| wp_options            |
| wp_postmeta           |
| wp_posts              |
| wp_term_relationships |
| wp_term_taxonomy      |
| wp_termmeta           |
| wp_terms              |
| wp_usermeta           |
| wp_users              |
+-----------------------+

This is a pretty minimal list; the old machine has a list 362 tables long! Matomo was a particularly egregious offender here.

With this information, I can use a script written by Mike Andreasen over on the WP Bullet website to dump the databases on the old machine:

# set WP-CLI flags
WPFLAGS="--allow-root"

# define path to the database dumps without trailing slash
DBSTORE="/tmp"
# get the name of the database
DBNAME=$(wp config get DB_NAME ${WPFLAGS})

# list all of the tables regardless of database prefix
TABLELIST=(wp_posts wp_postmeta)

# create the temporary directory for storing the dumps
mkdir -p ${DBSTORE}/${DBNAME}

# loop through tables and export, log details to /tmp/mysqlexport-<database>.txt
for TABLE in ${TABLELIST[@]}
do
    # export the table
    wp db export ${DBSTORE}/${DBNAME}/${TABLE}.sql --tables=${TABLE} ${WPFLAGS} | tee /dev/stderr
done > /tmp/mysqlexport-${DBNAME}.txt

With this done, I scp the files from the old machine to my local machine. Then I scp them up to the new machine. The next script assumes they are in the sql directory in the wordpress folder.

I tried it, but I should have taken a snapshot, first. 😉

I need to search-and-replace all instances of the old domain name in the MySQL dump files, and put in the new domain name. Technically, once the actual switch happens, the new machine will be found at the old name, so this shouldn’t be necessary. But, the whole reason for migrating to a development machine is to test out this migration process. And the new machine does have a different domain name.

The script to upload the MySQL dumps looks like this:

# define WordPress path
WPPATH="/var/www/html/wordpress"

# loop through all of the 
for DUMP in /var/www/html/wordpress/sql/*.sql;
do
    wp db import ${DUMP} --allow-root --path=${WPPATH}
done

But, until the data is cleaned up, the new WordPress website gets the dreaded white-screen-of-death.