Moving Redis Postgres directories to different disks

Redis and Postgres can get very large, so you probably need to move it off the root partition on servers (especially VMs)

The easiest way is to softlink the data dirs on a different partition to the standard location, so the config file doesn't need to change (and get wiped out during upgrades)

Redis

# as root user
service redis-server stop
mkdir /mnt/redis_database
chmod 755 /mnt/redis_database
chown redis /mnt/redis_database
mv /var/lib/redis/* /mnt/redis_database
rmdir /var/lib/redis
ln -s /mnt/redis_database /var/lib/redis

The service is restricted to what directories it can write to. So modify:

vi /lib/systemd/system/redis-server.service

Then add a line eg:

ReadWriteDirectories=-/mnt/redis_database

systemctl daemon-reload # Applies ReadWriteDirectories change above
sudo service redis-server start

Trouble shooting

To hard shutdown the server:

redis-cli
>shutdown NOSAVE

Make sure to check redis logs that backups work etc

tail -f /var/log/redis/redis-server.log

Postgres

Ran out of space on VM instance (10G), so moved to Ephemeral disk (120G)

#!bash

sudo bash

# as root
service postgresql stop
cd /var/lib/postgresql/9.4
cp -aRv main /mnt/postgresql
mv main main.OLD
su postgres
# as postgres
ln -s /mnt/postgresql main
# CTR+D to logout of postgres account
service postgresql start

# Note: Sometimes I have trouble with starting postgres, so use:
sudo systemctl start postgresql