Thank you for your quick response.
After reflection, it's perhaps when upgrading to 3.0.4 that the problem occurred (not the 18.104.22.168), I'm not sure...
I performed the operation suggested. I'm not sure the problem is fully resolved.
My test user is still not jailrooted.
One link is still dead (jk_socketd.ini)
# vdir /usr/jk*
lrwxrwxrwx 1 root root 24 27 nov. 16:40 /usr/jk_init.ini -> /etc/jailkit/jk_init.ini
lrwxrwxrwx 1 root root 27 27 nov. 16:40 /usr/jk_socketd.ini -> /etc/jailkit/jk_socketd.ini
# vdir /etc/jailkit/
-rw-r--r-- 1 root root 272 30 nov. 20:49 jk_chrootsh.ini
-rw-r--r-- 1 root root 5034 30 nov. 20:49 jk_init.ini
As I do not know exactly how it works, I do not want to mess up my system...
The jailkit used by ispconfig is there? http://olivier.sessink.nl/jailkit/
I'll try to delete my test user and create a new one.
Thank you for your help.
Edit: I tried... and failed.
# tail -f /var/log/auth.log |grep "usermod\|sshd"
usermod: change user 'test' shell from '/bin/bash' to '/bin/false'
usermod: lock user 'test' password
usermod: change user 'test' shell from '/bin/false' to '/usr/sbin/jk_chrootsh'
usermod: unlock user 'test' password
sshd: User test not allowed because shell /usr/sbin/jk_chrootsh does not exist
sshd: Failed none for invalid user test from 41.xxx.xxx.xxx port 1692 ssh2
sshd: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=my.domain.tld user=test
sshd: Failed password for invalid user test from 41.xxx.xxx.xxx port 1692 ssh2