Can't initialize Redis as a systemd service (supervised systemd) on Ubuntu Server 20.04.2

On Ubuntu Server 20.04, Redis (5.0.7) doesn't start after setting supervised systemd on /etc/redis/redis.conf, but no error is printed when running it manually with /usr/bin/redis-server /etc/redis/redis.conf.

Also, when running manually, its possible to find it listening on port 6379 with netstat -tulpn.

To reproduce

As root:

• Update packages and install Redis with apt update && apt install redis-server
• On /etc/redis/redis.conf, change the line with supervised no to supervised systemd
• Try to restart Redis with service redis-server restart or systemctl restart redis

The output of the above command is:

Job for redis-server.service failed because the control process exited with error code.
See "systemctl status redis-server.service" and "journalctl -xe" for details.

And the output of systemctl status redis-server.service is:

● redis-server.service - Advanced key-value store
     Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Wed 2021-02-03 12:15:56 -03; 28s ago
       Docs: http://redis.io/documentation,
             man:redis-server(1)
    Process: 3851 ExecStart=/usr/bin/redis-server /etc/redis/redis.conf (code=exited, status=1/FAILURE)

Feb 03 12:15:56 mywebsite.com systemd[1]: redis-server.service: Scheduled restart job, restart counter is at 5.
Feb 03 12:15:56 mywebsite.com systemd[1]: Stopped Advanced key-value store.
Feb 03 12:15:56 mywebsite.com systemd[1]: redis-server.service: Start request repeated too quickly.
Feb 03 12:15:56 mywebsite.com systemd[1]: redis-server.service: Failed with result 'exit-code'.
Feb 03 12:15:56 mywebsite.com systemd[1]: Failed to start Advanced key-value store.

No log is printed on /var/log/redis/redis-server.log when trying to restart Redis service, but the text below is printed when running it manually:

4231:C 03 Feb 2021 12:27:52.053 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
4231:C 03 Feb 2021 12:27:52.053 # Redis version=5.0.7, bits=64, commit=00000000, modified=0, pid=4231, just started
4231:C 03 Feb 2021 12:27:52.053 # Configuration loaded
4232:M 03 Feb 2021 12:27:52.063 * Increased maximum number of open files to 10032 (it was originally set to 1024).
                _._
           _.-``__ ''-._
      _.-``    `.  `_.  ''-._           Redis 5.0.7 (00000000/0) 64 bit
  .-`` .-```.  ```\/    _.,_ ''-._
 (    '      ,       .-`  | `,    )     Running in standalone mode
 |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
 |    `-._   `._    /     _.-'    |     PID: 4232
  `-._    `-._  `-./  _.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |           http://redis.io
  `-._    `-._`-.__.-'_.-'    _.-'
 |`-._`-._    `-.__.-'    _.-'_.-'|
 |    `-._`-._        _.-'_.-'    |
  `-._    `-._`-.__.-'_.-'    _.-'
      `-._    `-.__.-'    _.-'
          `-._        _.-'
              `-.__.-'

4232:M 03 Feb 2021 12:27:52.065 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
4232:M 03 Feb 2021 12:27:52.065 # Server initialized
4232:M 03 Feb 2021 12:27:52.066 * Ready to accept connections

Software versions:

Redis server v=5.0.7 sha=00000000:0 malloc=jemalloc-5.2.1 bits=64 build=636cde3b5c7a3923

Ubuntu 20.04.2 LTS - 64 bit

systemd 245 (245.4-4ubuntu3.4)

Solution 1:

It's pretty strange, but Ubuntu's installation of redis-server does not use redis's ability to communicate with systemd. On this platform you should leave redis.conf set as it shipped: supervised no.

If you really want to enable this for some reason, you will have to customize the systemd unit, for example:

ubuntu@vmtest-ubuntu2004:~$ sudo systemctl edit redis-server.service

In nano, you should add only this:

[Service]
Type=notify

Then tell systemd to load the changes.

ubuntu@vmtest-ubuntu2004:~$ sudo systemctl daemon-reload

Now you need to edit redis.conf:

ubuntu@vmtest-ubuntu2004:~$ sudo nano /etc/redis/redis.conf

And make these changes:

daemonize no
supervised systemd

Now you can restart redis-server:

ubuntu@vmtest-ubuntu2004:~$ sudo systemctl start redis-server
ubuntu@vmtest-ubuntu2004:~$ sudo systemctl status redis-server
* redis-server.service - Advanced key-value store
     Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled)
    Drop-In: /etc/systemd/system/redis-server.service.d
             `-override.conf
     Active: active (running) since Wed 2021-02-03 11:55:09 EST; 1min 8s ago
       Docs: http://redis.io/documentation,
             man:redis-server(1)
   Main PID: 1768 (redis-server)
      Tasks: 4 (limit: 2318)
     Memory: 1.8M
     CGroup: /system.slice/redis-server.service
             `-1768 /usr/bin/redis-server 127.0.0.1:6379

Feb 03 11:55:09 vmtest-ubuntu2004 systemd[1]: Starting Advanced key-value store...
Feb 03 11:55:09 vmtest-ubuntu2004 systemd[1]: Started Advanced key-value store.