Resolved Unable to create nextcloud jail with fail2ban

[Zoo3]

I use fail2ban and even more so, I use Nextcloud. I've been failing to start fail2ban since NC became version 18.
If I remove the Nextcloud item from fail2ban's jail on PLESK UI, fail2ban will start fine. I add Nextcloud to jail and it fails. I tried to set up jail.conf and filter.conf of people who can start fail2ban with NC18 in my conf respectively.

Previously, nextcloud Jail was inactive on the Plesk UI. When I set up a new conf file and restarted fail2ban(systemctl restart fail2ban), it changed to "active" on the Plesk UI. But when I look at the status(systemctl status fail2ban), fail2ban is failing.

```
● fail2ban.service - Fail2Ban Service
Loaded: loaded (/usr/lib/systemd/system/fail2ban.service; enabled; vendor preset: disabled)
Drop-In: /usr/lib/systemd/system/fail2ban.service.d
└─50-ensure-log.conf
Active: failed (Result: exit-code) since TIME; 3s ago
Docs: man:fail2ban(1)
Process: 10680 ExecStart=/usr/bin/fail2ban-server -xf start (code=exited, status=255)
Process: 10675 ExecStartPre=/bin/sh -c umask 077; touch /var/log/fail2ban.log; restorecon /var/log/fail2ban.log >/dev/null 2>&1 (code=exited, status=0/SUCCESS)
Process: 10673 ExecStartPre=/bin/mkdir -p /var/run/fail2ban (code=exited, status=0/SUCCESS)
Main PID: 10680 (code=exited, status=255)

AAAAAAAA systemd[1]: Started Fail2Ban Service.
AAAAAAAA fail2ban-server[10680]: TIME:41,546 fail2ban [10680]: ERROR Failed during configuration: Bad value substitution:
AAAAAAAA fail2ban-server[10680]: section: [nextcloud]
AAAAAAAA fail2ban-server[10680]: option : action
AAAAAAAA fail2ban-server[10680]: key : action_mwl
AAAAAAAA fail2ban-server[10680]: rawval :
AAAAAAAA fail2ban-server[10680]: TIME:41,551 fail2ban [10680]: ERROR Async configuration of server failed
AAAAAAAA systemd[1]: fail2ban.service: main process exited, code=exited, status=255/n/a
AAAAAAAA systemd[1]: Unit fail2ban.service entered failed state.
AAAAAAAA systemd[1]: fail2ban.service failed.

```

Below is a log of fail2ban.
```
fail2ban.server [16054]: INFO --------------------------------------------------
fail2ban.server [16054]: INFO Starting Fail2ban v0.10.3.fix1
fail2ban.database [16054]: INFO Connected to fail2ban persistent database '/var/lib/fail2ban/fail2ban.sqlite3'
fail2ban.server [16054]: INFO Shutdown in progress...
fail2ban.server [16054]: INFO Stopping all jails
fail2ban.database [16054]: INFO Connection to database closed.
fail2ban.server [16054]: INFO Exiting Fail2ban
```

I have tried reinstalling fail2ban, which is featured in Plesk's Knowledge. But it was not resolved.
There is no menu to set the "filter" in fail2ban on Plesk. How do I get fail2ban to start successfully?

Does Plesk have Plesk's own fail2ban in it? I didn't have to install FAIL2BAN in YUM, did I?

 

[Zoo3]

The filters required by Nextcloud are as follows
```
[Definition]
failregex = ^{“reqId”:".",“remoteAddr”:".",“app”:“core”,“message”:“Login failed: '.’ (Remote IP: ‘’)",“level”:2,“time”:".”}$
^{“reqId”:".",“level”:2,“time”:".",“remoteAddr”:".",“app”:“core”.",“message”:"Login failed: '.’ (Remote IP: ‘’)".}$
ignoreregex =
```

I gave up editing in SSH and tried to create filters only via SSH and jail in Plesk.
Then the following error is output.

```
f2bmng failed: TIME fail2ban [903]: ERROR NOK: ('No failure-id group in \'^{\xe2\x80\x9creqId\xe2\x80\x9d:".",\xe2\x80\x9cremoteAddr\xe2\x80\x9d:".",\xe2\x80\x9capp\xe2\x80\x9d:\xe2\x80\x9ccore\xe2\x80\x9d,\xe2\x80\x9cmessage\xe2\x80\x9d:\xe2\x80\x9cLogin failed: \'.\xe2\x80\x99 (Remote IP: \xe2\x80\x98\xe2\x80\x99)",\xe2\x80\x9clevel\xe2\x80\x9d:2,\xe2\x80\x9ctime\xe2\x80\x9d:".\xe2\x80\x9d}$\'',)
ERROR:__main__:Command '['/usr/bin/fail2ban-client', 'reload', '--if-exists', 'nextcloud']' returned non-zero exit status 255
ERROR:__main__:Failed to reload following jails due to errors in configuration: nextcloud
```

I then tried to select an existing filter. Then the following error is output.
```
f2bmng failed: TIME fail2ban [2366]: ERROR NOK: (13, 'Permission denied')
ERROR:__main__:Command '['/usr/bin/fail2ban-client', 'reload', '--if-exists', 'nextcloud']' returned non-zero exit status 255
ERROR:__main__:Failed to reload following jails due to errors in configuration: nextcloud
```

 

[Zoo3]

This was caused by SELinux.
I disabled SELinux, then reinstalled the "selinux-policy" association, then enabled SELinux. Then I was able to start fail2ban successfully.