KeepAlived service running but does not executes the check haproxy script

Question

I have configured a failover load balancer, so that it acts as a backup whenever my primary goes down. So I have setup Keepalived that switches the floating virtual IP address to the other machine whenever it is unable to find the service HAProxy running on other machine. The IP addresses mentioned in conf file are present on my eth1 interface.

On my primary load balancer I am getting

systemctl status keepalived

`● keepalived.service - Keepalive Daemon (LVS and VRRP)
     Loaded: loaded (/lib/systemd/system/keepalived.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2022-05-15 18:06:32 UTC; 21min ago
   Main PID: 659 (keepalived)
      Tasks: 2 (limit: 1131)
     Memory: 4.7M
     CGroup: /system.slice/keepalived.service
             ├─659 /usr/sbin/keepalived --dont-fork
             └─711 /usr/sbin/keepalived --dont-fork

May 15 18:27:57 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2250]: only one argument, a signal number, allowed
May 15 18:28:01 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2252]: only one argument, a signal number, allowed
May 15 18:28:03 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2253]: only one argument, a signal number, allowed
May 15 18:28:05 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2256]: only one argument, a signal number, allowed
May 15 18:28:07 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2259]: only one argument, a signal number, allowed
May 15 18:28:09 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2260]: only one argument, a signal number, allowed
May 15 18:28:11 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2261]: only one argument, a signal number, allowed
May 15 18:28:13 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2262]: only one argument, a signal number, allowed
May 15 18:28:15 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2263]: only one argument, a signal number, allowed
May 15 18:28:17 ubuntu-s-1vcpu-1gb-blr1-01 killall5[2264]: only one argument, a signal number, allowed`

sudo nano /etc/keepalived/keepalived.conf

`vrrp_script chk_haproxy {
    script "pidof haproxy"
    interval 2
}

vrrp_instance VI_1 {
    interface eth1
    state MASTER
    priority 200


virtual_router_id 33
    unicast_src_ip 10.122.0.2
    unicast_peer {
        10.122.0.3
    }


authentication {
        auth_type PASS
        auth_pass password
}

    track_script {
        chk_haproxy
    }

    notify_master /etc/keepalived/master.sh

}`

On my secondary load balancer

systemctl status keepalived

`` ● keepalived.service - Keepalive Daemon (LVS and VRRP) Loaded: loaded (/lib/systemd/system/keepalived.service; enabled; vendor preset: enabled) Active: active (running) since Sun 2022-05-15 17:57:16 UTC; 36min ago Main PID: 329993 (keepalived) Tasks: 2 (limit: 4677) Memory: 1.9M CGroup: /system.slice/keepalived.service ├─329993 /usr/sbin/keepalived --dont-fork └─330005 /usr/sbin/keepalived --dont-fork

May 15 17:57:16 ubuntu-s-2vcpu-4gb-blr1-01 Keepalived_vrrp[330005]: Script `chk_haproxy` now returning 1
May 15 17:57:16 ubuntu-s-2vcpu-4gb-blr1-01 Keepalived_vrrp[330005]: VRRP_Script(chk_haproxy) failed (exited with status 1)
May 15 17:57:16 ubuntu-s-2vcpu-4gb-blr1-01 Keepalived_vrrp[330005]: (VI_1) Entering FAULT STATE
May 15 18:05:21 ubuntu-s-2vcpu-4gb-blr1-01 killall5[330439]: only one argument, a signal number, allowed
May 15 18:10:13 ubuntu-s-2vcpu-4gb-blr1-01 killall5[330679]: only one argument, a signal number, allowed
May 15 18:11:37 ubuntu-s-2vcpu-4gb-blr1-01 killall5[330750]: only one argument, a signal number, allowed
May 15 18:17:53 ubuntu-s-2vcpu-4gb-blr1-01 killall5[331070]: only one argument, a signal number, allowed
May 15 18:24:21 ubuntu-s-2vcpu-4gb-blr1-01 killall5[331386]: only one argument, a signal number, allowed
May 15 18:28:11 ubuntu-s-2vcpu-4gb-blr1-01 killall5[331552]: only one argument, a signal number, allowed
May 15 18:30:31 ubuntu-s-2vcpu-4gb-blr1-01 killall5[331649]: only one argument, a signal number, allowed``

sudo nano /etc/keepalived/keepalived.conf

`vrrp_script chk_haproxy {
    script "pidof haproxy"
    interval 2
}

vrrp_instance VI_1 {
    interface eth1
    state BACKUP
    priority 100


virtual_router_id 33
    unicast_src_ip 10.122.0.3
    unicast_peer {
        10.122.0.2
    }


authentication {
        auth_type PASS
        auth_pass password
    }

    track_script {
        chk_haproxy
    }

    notify_master /etc/keepalived/master.sh
}

Output of pidofpidof haproxy`

Primary

root@ubuntu-s-1vcpu-1gb-blr1-01:~# pidof haproxy
726 719

Secondary

root@ubuntu-s-2vcpu-4gb-blr1-01:~# pidof haproxy
328842 328841

Note : I ran the /etc/keepalived/master.sh script manually and it was working successfully.

EDIT1: It does not work even when I use pidof -s haproxy

Bobby · Answer

Hi there, I might be missing something, but this looks less like Keepalived not running the check and more like how the check script exit code is handled. vrrp_script only cares about the exit status. pidof haproxy returns 0 if it finds a PID and 1 if it doesn’t, which is fine in theory, but in practice this can break if the command behaves slightly differently under Keepalived’s execution environment. A couple of things that usually trip people up here: Keepalived runs scripts with a very minimal environment. Using a bare command like pidof without a full path can fail. Try /bin/pidof haproxy. It’s often safer to wrap the check in a small shell script that explicitly returns 0 or 1, rather than calling pidof inline. Make sure the script is executable and owned by root. The repeated killall5 messages are usually unrelated noise from systemd shutdown checks, not the root cause. In most setups, changing the script to something like a simple shell check (pgrep haproxy > /dev/null || exit 1) with a full path resolves this. If it still behaves oddly, enabling Keepalived debug logging can help confirm whether the script is actually being executed and what exit code it returns.

alexdo · Answer

Heya, Those killall5: only one argument, a signal number, allowed lines aren’t coming from Keepalived’s VRRP logic itself — they’re almost always coming from your notify_master /etc/keepalived/master.sh script being triggered and then calling killall5 incorrectly (for example, passing it a PID or a process name instead of a signal number). So you’ve basically got two separate things going on: First, fix master.sh . Don’t use killall5 here. If you’re trying to restart HAProxy, use systemctl restart haproxy (or service haproxy restart). If you’re trying to kill PIDs from pidof, use kill -TERM $(pidof haproxy) (or pkill -TERM -x haproxy). Once you remove the bad killall5 usage, that spam should stop. Second, your secondary entering FAULT means chk_haproxy returned non-zero at the moment Keepalived ran it. Even if pidof haproxy works when you run it manually, Keepalived can still fail it if the command path/environment differs. The simplest fix is to use an explicit full path and a more predictable check, e.g.: script “/usr/bin/pgrep -x haproxy >/dev/null 2>&1” (or /bin/pidof haproxy >/dev/null 2>&1 if that’s where pidof lives on your distro). After changing those, restart Keepalived on both nodes and watch journalctl -u keepalived -f , you should see the script stop failing and the FAULT state go away.

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KeepAlived service running but does not executes the check haproxy script

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KeepAlived service running but does not executes the check haproxy script

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