Posts Tagged ‘weird’

Deny DHCP Address by MAC on Linux

Thursday, October 8th, 2020

Deny DHCP addresses by MAC ignore MAC to not be DHCPD leased on GNU / Linux howto

I have not blogged for a long time due to being on a few weeks vacation and being in home with a small cute baby. However as a hardcore and a bit of dumb System administrator, I have spend some of my vacation and   worked on bringing up the the www.pc-freak.net and the other Websites hosted as a high availvailability ones living on a 2 Webservers running on a Master to Master MySQL Replication backend database, this is oll hosted on  servers, set to run as a round robin DNS hosts on 2 servers one old Lenove ThinkCentre Edge71 as well as a brand new real Lenovo server Lenovo ThinkServer SD350 with 24 CPUs and a 32 GB of RAM
To assure Internet Connectivity is having a good degree of connectivity and ensure websites hosted on both machines is not going to die if one of the 2 pair configured Fiber Optics Internet Providers Bergon.NET has some Issues, I've rented another Internet Provider Line is set bought from the VIVACOM Mobile Fiber Internet provider – that is a 1 Gigabit Fiber Optics Line.
Next to that to guarantee there is no Database, Webserver, MailServer, Memcached and other running services did not hit downtimes due to Electricity power outage, two Powerful Uninterruptable Power Supplies (UPS)  FPS Fortron devices are connected to the servers each of which that could keep the machine and the connected switches and Servers for up to 1 Hour.

The machines are configured to use dhcpd to distributed IP addresses and the Main Node is set to distribute IPs, however as there is a local LAN network with more of a personal Work PCs, Wireless Devices and Testing Computers and few Virtual machines in the Network and the IPs are being distributed in a consequential manner via a ISC DHCP server.

As always to make everything work properly hence, I had again some a bit weird non-standard requirement to make some of the computers within the Network with Static IP addresses and the others to have their IPs received via the DHCP (Dynamic Host Configuration Protocol) and add some filter for some of the Machine MAC Addresses which are configured to have a static IP addresses to prevent the DHCP (daemon) server to automatically reassign IPs to this machines.

After a bit of googling and pondering I've done it and some of the machines, therefore to save others the efforts to look around How to set Certain Computers / Servers Network Card MAC (Interfaces) MAC Addresses  configured on the LAN network to use Static IPs and instruct the DHCP server to ingnore any broadcast IP addresses leases – if they're to be destined to a set of IGNORED MAcs, I came up with this small article.

Here is the DHCP server /etc/dhcpd/dhcpd.conf from my Debian GNU / Linux (Buster) 10.4

 

option domain-name "pcfreak.lan";
option domain-name-servers 8.8.8.8, 8.8.4.4, 208.67.222.222, 208.67.220.220;
max-lease-time 891200;
authoritative;
class "black-hole" {
    match substring (hardware, 1, 6);
    ignore booting;
}
subclass "black-hole" 18:45:91:c3:d9:00;
subclass "black-hole" 70:e2:81:13:44:11;
subclass "black-hole" 70:e2:81:13:44:12;
subclass "black-hole" 00:16:3f:53:5d:11;
subclass "black-hole" 18:45:9b:c6:d9:00;
subclass "black-hole" 16:45:93:c3:d9:09;
subclass "black-hole" 16:45:94:c3:d9:0d;/etc/dhcpd/dhcpd.conf
subclass "black-hole" 60:67:21:3c:20:ec;
subclass "black-hole" 60:67:20:5c:20:ed;
subclass "black-hole" 00:16:3e:0f:48:04;
subclass "black-hole" 00:16:3e:3a:f4:fc;
subclass "black-hole" 50:d4:f5:13:e8:ba;
subclass "black-hole" 50:d4:f5:13:e8:bb;
subnet 192.168.0.0 netmask 255.255.255.0 {
        option routers                  192.168.0.1;
        option subnet-mask              255.255.255.0;
}
host think-server {
        hardware ethernet 70:e2:85:13:44:12;
        fixed-address 192.168.0.200;
}
default-lease-time 691200;
max-lease-time 891200;
log-facility local7;

To spend you copy paste efforts a file with Deny DHCP Address by Mac Linux configuration is here
/home/hipo/info
Of course I have dumped the MAC Addresses to omit a data leaking but I guess the idea behind the MAC ADDR ignore is quite clear

The main configuration doing the trick to ignore a certain MAC ALenovo ThinkServer SD350ddresses that are reachable on the Connected hardware switch on the device is like so:

class "black-hole" {
    match substring (hardware, 1, 6);
    ignore booting;
}
subclass "black-hole" 18:45:91:c3:d9:00;


The Deny DHCP Address by MAC is described on isc.org distribution lists here but it seems the documentation on the topic on how to Deny / IGNORE DHCP Addresses by MAC Address on Linux has been quite obscure and limited online.

As you can see in above config the time via which an IP is freed up and a new IP lease is done from the server is severely maximized as often DHCP servers do use a max-lease-time like 1 hour (3600) seconds:, the reason for increasing the lease time to be to like 10 days time is that the IPs in my network change very rarely so it is a waste of CPU cycles to do a frequent lease.

default-lease-time 691200;
max-lease-time 891200;


As you see to Guarantee resolving works always as expected I have configured – Google Public DNS and OpenDNS IPs

option domain-name-servers 8.8.8.8, 8.8.4.4, 208.67.222.222, 208.67.220.220;


One hint to make is, after setting up all my desired config in the standard config location /etc/dhcp/dhcpd.conf it is always good idea to test configuration before reloading the running dhcpd process.

 

root@pcfreak: ~# /usr/sbin/dhcpd -t
Internet Systems Consortium DHCP Server 4.4.1
Copyright 2004-2018 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Config file: /etc/dhcp/dhcpd.conf
Database file: /va/home/hipo/infor/lib/dhcp/dhcpd.leases
PID file: /var/run/dhcpd.pid
 

That's all folks with this sample config the IPs under subclass "black-hole", which are a local LAN Static IP Addresses will never be offered leasess anymore from the ISC DHCP.
Hope this stuff helps someone, enjoy and in case if you need a colocation of a server or a website hosting for a really cheap price on this new set High Availlability up described machines open an inquiry on https://web.pc-freak.net.

 

Fixing weird problems with missing File Explorer on Polaroid MPCS700 tablet with Andorid 2.2 (Linux kernel 2.6.32)

Wednesday, October 10th, 2012

Polaroid MPCs700 Tablet Android version 2.2 with 2.6.32 linux kernel picture

I’ve been given Android Polaroid Tablet which had only 5 clickable icons on main (touchscreen) display:

  • Settings
  • Wi-Fi Settings
  • Youtube
  • Browser
  • App market

The shipped in standard applications for Listening Music, Watching Videos, Managing Photos and Browsing files / ( My Photo, My Video, My Music, File Browser) were missing.

Main problem was File Browser by default shipped with Anroid was missing, and if an USB Stick / Flash Drive is plugged in to the USB port, a message appears along with a sound indicating the USB Flash Drive is detected but there was no way to access the USB Flash drive data ….

The tablet is a second hand bought one and is not my own and it appeared like someone has messed up with it trying to change default Android Linux kernel with some “hacked” (custom compiled one?).

The exact Android version installed on it is 2.2, I checked navigating to:


Settings -> About Device

Android 2.2 Polaroid Settings About Device Screenshot pic

Onwards to fix the messed android I had to reset the device to its factory settings by navigating to:


Settings -> Privacy -> Factory data reset

Android 2.2 Polaroid Settings Privacy Reset to Factory Defaults Screenshot

This formats the device and all installed programs and restores the kernel to its original version, so after few minutes of waiting all worked like a charm 🙂

The normal programs for viewing pics, listening music, File Explorer all come at place. Even both VFAT (Fat 32) and NTFS formatted USB drives file systems worked normally with the device. Before that I was puzzled because I suspected the USB Drive is not detected because the kernel is not supporting NTFS and I need to install something. I was wrong just this Factory data reset and NTFS USB bundled by default works as usual 🙂

Fix weird problem with Apache default encoding (AddDefaultCharset) not taking effect on FreeBSD with Apache version (2.0.63)

Tuesday, March 23rd, 2010

I encountered a weird problems a couple of minutes before. I tried to put some text files written in UTF-8 which contain cyrillic in the file names as well as the content the files has in my Apache directory listing. Trying that produced a lot of “alien symbols” for both file names and file content.
I have to admit that wasn’t exactly what I expected. I’ve checked my /usr/local/etc/apache/httpd.conf just to find out I already have the:

AddDefaultCharset utf-8

within in the configuration, I thought that somehow Apache could have difficulties applying that rules for the custom Virtualhost and therefore give the directive a try locally in the VirtualHost. Grievously that didn’t produced any positive result. That’s why I decided to check if somebody has experienced the same weird behavior and I stumbled on this wondeful blog post .
In short on the plug and pray’s blog … Wait and moment plug and pray? Yes you read that correctly it’s plug and pray :), on that blog it’s explained that newer versions of Apache 2.2.4 as this is the version the blogger talks about as well as the latest Apache release has an issue with AddDefaultCharset not working anymore. Fortunately the issue with the AddDefaultCharset not taking effect in Apache no more is easily solved. All that needs to be done is including the:

IndexOptions Charset=UTF-8

Within Apache conf file. In my case on FreeBSD I had to include that in /usr/local/etc/apache2/httpd.conf after which all worked perfectly fine and I can see all my cyrillic symbols showing anew.

Weird Delux 5201 keyboard problems on Linux

Thursday, October 22nd, 2009

I own the shitty Delux 5201 keyboard. On Current Debian Testing/Unstable,a weird keyboard problem occurs. The problem consists in “wsx” keys, refusingto work. It’s really annoying, sometimes all the keyboard keys work, other timesthey don’t … Complete insanity!