Upgrade PostgreSQL 9.6.5 to 10.0 using Homebrew (macOS)

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After automatically updating Postgres to 10.0 via Homebrew, the pg_ctl start command didn't work.
The error was "The data directory was initialized by PostgreSQL version 9.6, which is not compatible with this version 10.0."

Database files have to be updated before starting the server, here are the steps that had to be followed:

# need to have both 9.6.x and latest 10.0 installed, and keep 10.0 as default
brew unlink postgresql
brew install [email protected]
brew unlink [email protected]
brew link postgresql

# move 9.6.x db files to another directory
mv /usr/local/var/postgres /usr/local/var/postgres96

# init new database using 10.0
initdb /usr/local/var/postgres -E utf8

# make timezone and timezonesets directories available for 9.6.x installation
mkdir /usr/local/share/postgresql96
cp -r /usr/local/share/postgresql/timezone /usr/local/share/postgresql96
cp -r /usr/local/share/postgresql/timezonesets /usr/local/share/postgresql96

# finally the actual upgrade
# -b is the old binary dir, -B is the new binary dir
# -d is the old data dir, -D is the new data dir
pg_upgrade -b /usr/local/Cellar/[email protected]/9.6.5/bin -B /usr/local/Cellar/postgresql/10.0/bin -d /usr/local/var/postgres96 -D /usr/local/var/postgres

# start 10.0 to check that upgrade works
pg_ctl start -D /usr/local/var/postgres

# cleanup if upgrade was successful
brew uninstall [email protected]
rm -rf /usr/local/var/postgres96
rm -rf /usr/local/share/postgresql96

Thank you.

One comment in my experience on this issue, at the very end, I had to run:

brew services stop postgresql
pg_ctl -D /usr/local/var/postgres stop
kill $postmaster_pid.
brew services restart postgresql

one after another in order to get rid of the following log repeating every 10s in postgres.log file:

2019-03-25 16:27:58.534 EET [18563] FATAL: lock file "postmaster.pid" already exists
2019-03-25 16:27:58.534 EET [18563] HINT: Is another postmaster (PID 14070) running in data directory "/usr/local/var/postgres"?

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Credits for finding the PID of postmaster.pid:
StackExchange

thanks. it's working. i like this.