Possible update scripts and their sequence, always run as root:

• pre_update.sh runs (if exists)
• Following this, pip install pioreactor...whl runs
• update.sh runs (if exists)
• update.sql to update sqlite schema runs (if exists)
• post_update.sh runs (if exists). Useful for restarting jobs, adding data to new db tables, or rebooting RPis.

It's very important that update scripts are idempotent. Some tips:

• Use ChatGPT to inspect if a script is idempotent, or make suggestions.

• the scripts are run as root user, so pios sync-configs fails with auth problems. Use sudo -u pioreactor pios sync-configs
• use || : if a command may fail, but you want to continue anyways
• use trap and EXIT semantics (like try / expect) to force some code block to always run.
• https://arslan.io/2019/07/03/how-to-write-idempotent-bash-scripts/

# Get the hostname
HOSTNAME=$(hostname)

# Get the leader hostname
# Don't use `leader_address`, as users do change that.
LEADER_HOSTNAME=$(crudini --get $PIO_DIR/config.ini cluster.topology leader_hostname)

if [ "$HOSTNAME" = "$LEADER_HOSTNAME" ]; then
  ...
fi

• use IF EXISTS