Posts Tagged ‘Disabling’

How to disable haproxy log for certain frontend / backend or stop haproxy logging completely

Wednesday, September 14th, 2022


In my previous article I've shortly explained on how it is possible to configure multiple haproxy instances to log in separate log files as well as how to configure a specific frontend to log inside a separate file. Sometimes it is simply unnecessery to keep any kind of log file for haproxy to spare disk space or even for anonymity of traffic. Hence in this tiny article will explain how to disable globally logging for haproxy and how logging for a certain frontend or backend could be stopped.

1. Disable globally logging of haproxy service

Disabling globally logging for haproxy in case if you don't need the log is being achieved by redirecting the log variable to /dev/null handler and to also mute the reoccurring alert, notice and info messages, that are produced in case of some extra ordinary events during start / stop of haproxy or during mising backends etc. you can send those messages to local0 and loca1 handlers which will be discarded later by rsyslogd configuration, for example thsi can be achieved with a configuration like:

global     log /dev/log    local0 info alert     log /dev/log    local1 notice alert  defaults log global mode http option httplog option dontlognull


<level>    is optional and can be specified to filter outgoing messages. By
           default, all messages are sent. If a level is specified, only
           messages with a severity at least as important as this level
           will be sent. An optional minimum level can be specified. If it
           is set, logs emitted with a more severe level than this one will
           be capped to this level. This is used to avoid sending "emerg"
           messages on all terminals on some default syslog configurations.
           Eight levels are known :
             emerg  alert  crit   err    warning notice info  debug


By using the log level you can also tell haproxy to omit from logging errors from log if for some reasons haproxy receives a lot of errors and this is flooding your logs, like this:

    backend Backend_Interface
  http-request set-log-level err
  no log

But sometimes you might need to disable it for a single frontend only and comes the question.

2. How to disable logging for a single frontend interface?

I thought that might be more complex but it was pretty easy with the option dontlog-normal haproxy.cfg variable:

Here is sample configuration with frontend and backend on how to instrucruct the haproxy frontend to disable all logging for the frontend

frontend ft_Frontend_Interface
#        log local4 debug
option dontlog-normal
        mode tcp
        option tcplog

              timeout client 350000
        log-format [%t]\ %ci:%cp\ %fi:%fp\ %b/%s:%sp\ %Tw/%Tc/%Tt\ %B\ %ts\ %ac/%fc/%bc/%sc/%rc\ %sq/%bq
        default_backend bk_WLP_echo_port_service

backend bk_Backend_Interface
                        timeout server 350000
                        timeout connect 35000
        server serverhost1 weight 1 check port 12345
        server serverhost2 weight 3 check port 12345


As you can see from those config, we have also enabled as a check port 12345 which is the application port service if something goes wrong with the application and 12345 is not anymore responding the respective server will get excluded automatically by haproxy and only one of machines will serve, the weight tells it which server will have the preference to serve the traffic the weight ratio will be 1 request will end up on one machine and 3 requests on the other machine.

3. How to disable single configured backend to not log anything but still have a log for the frontend

Omit the use of option dontlog normal from frontend inside the backend just set  no log:

backend bk_Backend_Interface
 no log
                        timeout server 350000
                        timeout connect 35000
        server serverhost1 weight 1 check port 12345
        server serverhost2 weight 3 check port 12345

That's all reload haproxy service on the machine and backend will no longer log to your default configured log file via the respective local0 – local6 handler.

How to disable IPv6 on Debian / Ubuntu / CentOS and RHEL Linux

Friday, December 9th, 2011

I have few servers, which have automatically enabled IPv6 protocols (IPv6 gets automatically enabled on Debian), as well as on most latest Linux distribituions nowdays.

Disabling IPv6 network protocol on Linux if not used has 2 reasons:

1. Security (It’s well known security practice to disable anything not used on a server)
Besides that IPv6 has been known for few criticil security vulnerabilities, which has historically affected the Linux kernel.
2. Performance (Sometimes disabling IPv6 could have positive impact on IPv4 especially on heavy traffic network servers).
I’ve red people claiming disabling IPv6 improves the DNS performance, however since this is not rumors and did not check it personally I cannot positively confirm this.

Disabling IPv6 on all GNU / Linuces can be achieved by changing the kernel sysctl settings net.ipv6.conf.all.disable_ipv6 by default net.ipv6.conf.all.disable_ipv6 equals 1 which means IPv6 is enabled, hence to disable IPv6 I issued:

server:~# sysctl net.ipv6.conf.all.disable_ipv6=0

To set it permanently on system boot I put the setting also in /etc/sysctl.conf :

server:~# echo 'net.ipv6.conf.all.disable = 1 >> /etc/sysctl.conf

The aforedescribed methods should be working on most Linux kernels version > 2.6.27 in that number it should work 100% on recent versions of Fedora, CentOS, Debian and Ubuntu.

To disable IPv6 protocol on Debian Lenny its necessery to blackist the ipv6 module in /etc/modprobe.d/blacklist by issuing:

echo 'blacklist ipv6' >> /etc/modprobe.d/blacklist

On Fedora / CentOS there is a another universal “Redhat” way disable IPv6.

On them disabling IPv6 is done by editting /etc/sysconfig/network and adding:


I would be happy to hear how people achieved disabling the IPv6, since on earlier and (various by distro) Linuxes the way to disable the IPv6 is probably different.

Alto to stop Iptables IPV6 on CentOS / Fedora and RHEL issue:

# service ip6tables stop

# service ip6tables off

Disabling sound kernel modules on Debian and Ubuntu GNU / Linux servers

Friday, October 19th, 2012

First step is to list modules related to sound (snd):

root@pcfreak:/var/www# lsmod|grep -i snd
snd_hda_codec_realtek 235234 1
snd_hda_intel 20035 0
snd_hda_codec 53940 2 snd_hda_codec_realtek,snd_hda_intel
snd_hwdep 5220 1 snd_hda_codec
snd_pcm_oss 32415 0
snd_mixer_oss 12478 1 snd_pcm_oss
snd_pcm 60151 3 snd_hda_intel,snd_hda_codec,snd_pcm_oss
snd_seq_midi 4256 0
snd_rawmidi 15323 1 snd_seq_midi
snd_seq_midi_event 4628 1 snd_seq_midi
snd_seq 41281 2 snd_seq_midi,snd_seq_midi_event
snd_timer 15502 2 snd_pcm,snd_seq
snd_seq_device 4493 3 snd_seq_midi,snd_rawmidi,snd_seq
snd 45998 11
soundcore 4566 1 snd
snd_page_alloc 6217 2 snd_hda_intel,snd_pcm

Then snd modules could be removed from current live system, for my Intel RealTek SoundBlaster, I had to remove following modules in (remove) order as follows:

root@pcfreak:/var/www# rmmod soundcore
ERROR: Module soundcore is in use by snd
root@pcfreak:/var/www# rmmod snd_hda_codec_realtec
ERROR: Module snd_hda_codec_realtec does not exist in /proc/modules
root@pcfreak:/var/www# rmmod snd_hda_intel
root@pcfreak:/var/www# rmmod snd_hda_codec
ERROR: Module snd_hda_codec is in use by snd_hda_codec_realtek
root@pcfreak:/var/www# rmmod snd_hda_codec_realtek
root@pcfreak:/var/www# rmmod snd_hda_codec
root@pcfreak:/var/www# rmmod snd_pcm_oss
root@pcfreak:/var/www# rmmod snd_seq_midi
root@pcfreak:/var/www# rmmod snd_rawmidi
root@pcfreak:/var/www# rmmod snd_seq_midi_event
root@pcfreak:/var/www# rmmod snd_seq
root@pcfreak:/var/www# rmmod snd_timer
ERROR: Module snd_timer is in use by snd_pcm
root@pcfreak:/var/www# rmmod snd_seq_device
root@pcfreak:/var/www# rmmod snd_pcm
root@pcfreak:/var/www# rmmod snd_seq_device
ERROR: Module snd_seq_device does not exist in /proc/modules
root@pcfreak:/var/www# rmmod snd_hda_intel
ERROR: Module snd_hda_intel does not exist in /proc/modules
rmmod snd_hwdep
root@pcfreak:/var/www# rmmod snd_mixer_oss
root@pcfreak:/var/www# rmmod snd_timer
root@pcfreak:/var/www# rmmod snd
root@pcfreak:/var/www# rmmod soundcore

Next step is to permanently disable all (blacklist) on system boot time loaded kernel modules, to do so in file /etc/modprobe.d/snd-bkaclist.conf, put:

blacklist soundcore
blacklist snd
blacklist snd_pcm
blacklist snd_pcsp
blacklist pcspkr

You can do it from shell ‘echo’-ing into file, like so:

# touch /etc/modprobe.d/snd-blacklist.conf
# cd /etc/modprobe.d/
# echo ‘blacklist soundcore’ >> snd-blacklist.conf
# echo ‘blacklist snd’ >> snd-blacklist.conf
# echo ‘blacklist snd_pcm’ >> snd-blacklist.conf
# echo ‘blacklist snd_pcsp’ >> snd-blacklist.conf
# echo ‘blacklist pcspkr’ >> snd-blacklist.conf

Another way is to use a tiny shellscript containing all previously shown rmmod commands and set the script to be executed via /etc/rc.local by adding the rmmod modules script, before exit 0 rc.local line.

Shell script removing my Realtek ICH sound driversis here
If you like to use it download it in /usr/local/bin or somewhere and invoke it via rc.local.
Removing sound blaster kernel support does not impact the overall machine performance, but in terms of security. Having sound driver modules constantly loaded in memory is a point which a possible attacker can use to root the host, so in my view always sound driver support should be removed.
Well that’s it hope this post helps someone 🙂

How to disable PC Speaker on FreeBSD / Mute PC-Speaker on BSD kernels

Wednesday, May 16th, 2012


old school personal computer pc speaker / freebsd disable Pc-Speaker picture

After finding out How PC Speaker is muted on Linux , I've decided to also disable the annoying beeps on BSD. This is in tandem with the minimalistic philosophy I try to apply to every server I manage.

Also on BSD Desktop machines it is quite annoying especially if csh (C Shell) is used, everytime you press TAB you get the beep sound. On BSD beep sound produced on tab completion is louder than in Linux and that makes it even more annoying …

Disabling pc-speaker beeps on BSDs is done via a sysctl kernel variable:

freebsd# sysctl hw.syscons.bell=0
hw.syscons.bell: 0 -> 0

To further permanently disable on system boot add hw.syscons.bell=0 to /etc/sysctl.conf, e.g.:

freebsd# echo 'hw.syscons.bell=0' >> /etc/sysctl.conf


Well that's it no more mind drilling beeps :)


Disabling php execution for a VirtualHost

Saturday, February 6th, 2010

Disabling php execution for a certain virtual domain is incredibly simple:
All you need to do is add:

php_value engine off

That could be anywhere in your VirtualHost directives.
Another possible approach is through enabling .htaccess for a domain, e.g.:

AllowOverride All to your domain of choice.

After which you had to put:
php_flag engine off to htaccess file
Now there you go! php scripts won’t execute anymore.