The post-install step did not complete successfully MySQL Mac OS Sierra

Question

[(pyEnv) Anants-MacBook-Pro:litibackend anantchandra$ brew postinstall mysql
==> Postinstalling mysql
==> /usr/local/Cellar/mysql/8.0.11/bin/mysqld --initialize-insecure --user=anantchandra --basedir=/usr/local/Cellar/mysql/8.0.11 --datadir=/usr/local/var/mysql --tmpdir=/tmp
Last 15 lines from /Users/anantchandra/Library/Logs/Homebrew/mysql/post_install.01.mysqld:
2018-06-15 04:41:04 -0700

/usr/local/Cellar/mysql/8.0.11/bin/mysqld
--initialize-insecure
--user=anantchandra
--basedir=/usr/local/Cellar/mysql/8.0.11
--datadir=/usr/local/var/mysql
--tmpdir=/tmp

2018-06-15T11:41:04.901191Z 0 [System] [MY-013169] [Server] /usr/local/Cellar/mysql/8.0.11/bin/mysqld (mysqld 8.0.11) initializing of server in progress as process 37841
2018-06-15T11:41:04.903504Z 0 [ERROR] [MY-010457] [Server] --initialize specified but the data directory has files in it. Aborting.
2018-06-15T11:41:04.903537Z 0 [ERROR] [MY-010119] [Server] Aborting
2018-06-15T11:41:04.903701Z 0 [System] [MY-010910] [Server] /usr/local/Cellar/mysql/8.0.11/bin/mysqld: Shutdown complete (mysqld 8.0.11)  Homebrew.

Warning: The post-install step did not complete successfully
You can try again using `brew postinstall mysql`

Answer 1

First, backup the content of your data directory: /usr/local/var/mysql by copying it to a safe place.

The error happens because the post-install script check if a file /usr/local/var/mysql/mysql/user.frm exists. For whatever reason you don't have this file. The postinstall script then tries to install a new MySQL 8 database by running mysqld with --initialize-insecure but as the directory already contains some data from MySQL 5.7 the script halts.

Here is the correspoding part of the script in mysql.rb:

  def post_install
    # Make sure the datadir exists
    datadir.mkpath
    unless (datadir/"mysql/user.frm").exist?
      ENV["TMPDIR"] = nil
      system bin/"mysqld", "--initialize-insecure", "--user=#{ENV["USER"]}",
        "--basedir=#{prefix}", "--datadir=#{datadir}", "--tmpdir=/tmp"
    end
  end

There is several possible solutions. If you can still run your MySQL 5.7 database, export everything with mysqldump then install a fresh MySQL 8 database by removing all content in /usr/local/var/mysql and then import everything back again. Another solution, is to use the mysql_upgrade tool.

P.S.: Personally, I use the formula [email protected] and I will in the future switch to MariaDB.

Answer 2

According to this link, below command saves me on macOS Mojave:

sudo chown -R $(whoami) /usr/local/*