Connection refused after update the agent

Troubleshooting
1

CMK version: 2.1.0-1
OS version: CentOS 8

Hi,

After update the agent on a client I get a connection refused error. How can I troubleshoot this error?
This is my procedure and the error:

Error message:

[root@CMK01 tmp]# rpm -ivh check-mk-agent-2.1.0-1.noarch.rpm
Verifying...                          ################################# [100%]
Preparing...                          ################################# [100%]
Updating / installing...
   1:check-mk-agent-2.1.0-1           ################################# [100%]

Deploying systemd units: cmk-agent-ctl-daemon.service check-mk-agent.socket check-mk-agent@.service check-mk-agent-async.service
Deployed systemd
Creating/updating cmk-agent user account ...
Reloading xinetd
Redirecting to /bin/systemctl reload xinetd.service
Activating systemd unit 'cmk-agent-ctl-daemon.service'...
Created symlink /etc/systemd/system/multi-user.target.wants/cmk-agent-ctl-daemon.service → /usr/lib/systemd/system/cmk-agent-ctl-daemon.service.
Activating systemd unit 'check-mk-agent.socket'...
Created symlink /etc/systemd/system/sockets.target.wants/check-mk-agent.socket → /usr/lib/systemd/system/check-mk-agent.socket.
Activating systemd unit 'check-mk-agent-async.service'...
Created symlink /etc/systemd/system/multi-user.target.wants/check-mk-agent-async.service → /usr/lib/systemd/system/check-mk-agent-async.service.
[root@CMK01 tmp]#
[root@CMK01 tmp]#
[root@CMK01 tmp]# telnet localhost 6556
Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Connection refused

[root@CMK01 tmp]# cat /etc/xinetd.d/check_mk.rpmsave | egrep -v '^#|#|^$'
service check_mk
{
        type           = UNLISTED
        port           = 6556
        socket_type    = stream
        protocol       = tcp
        wait           = no
        user           = root
        server         = /usr/bin/check_mk_agent
        per_source     = 3
        flags          = IPv4
        log_on_success =
        disable        = no
}

Also I see on message error this line:

May 31 09:09:59 CMK01 cmk-agent-ctl[1907624]: ERROR [cmk_agent_ctl] Address family not supported by protocol (os error 97)

How can I start/enable the agent?
thanks in advance

2

Please provide the output of:

systemctl --version
ss -tulpn | grep 6556

In case you disabled IPv6 you might use xinetd as a temporary workaround until p1 is available.

This might be the temporary solution: Agent Problems after update to 2.1.0 - #9 by mschlenker

3

no 6556 available. This is the problem…
wow! there’s a bug. Ok… I can wait for the next release because actually my server don’t have ipv6 activated.

4

Please check whether installing the 2.1.0p1 fixes the problem for you.

5

Got the same problem. @mschlenker also on 2.1.0.p1

6

Also ipv6 disabled by boot parameter? In this case please revert to the 2.0.0 agent or enable xinetd mode for now. We are investigating the problem.

7

Yes, ipv6 disabled:

GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX="ipv6.disable=1"

the 2.0 agent works for now

8

Let me guess: Kernel 5.4 or earlier? Booting without disabling IPv6 on the kernel command line and disabling during boot with sysctl might work around the problem, but a proper fix is on the way.

9

Yes, Kernalversion 4.15.0

10

Just hit this one, too. We’ve got a couple of systems running Ubuntu 18.04 LTS that uses Linux 4.15 and have the IPv6 Stack disabled.

11

let me know when the fix is available

12

I am also interested about the fix. We have some areas where we can’t just enable IPv6 to fix this.

13

Hi,
thanks for reporting this, the issue has been fixed: Agent controller: Fix agent data transport for IPv4-only hosts
Best, Jörg

2 Likes
14

This topic was automatically closed 365 days after the last reply. New replies are no longer allowed. Contact an admin if you think this should be re-opened.