Posts Tagged ‘occured’

‘host-name’ is blocked because of many connection errors; unblock with ‘mysqladmin flush-hosts’

Sunday, May 20th, 2012

Reading Time: 3minutes

mysql-logo-host-name-blocked-because-of-many-connection-errors
My home run machine MySQL server was suddenly down as I tried to check my blog and other sites today, the error I saw while trying to open, this blog as well as other hosted sites using the MySQL was:

Error establishing a database connection

The topology, where this error occured is simple, I have two hosts:

1. Apache version 2.0.64 compiled support externally PHP scripts interpretation via libphp – the host runs on (FreeBSD)

2. A Debian GNU / Linux squeeze running MySQL server version 5.1.61

The Apache host is assigned a local IP address 192.168.0.1 and the SQL server is running on a host with IP 192.168.0.2

To diagnose the error I've logged in to 192.168.0.2 and weirdly the mysql-server was appearing to run just fine:
 

debian:~# ps ax |grep -i mysql
31781 pts/0 S 0:00 /bin/sh /usr/bin/mysqld_safe
31940 pts/0 Sl 12:08 /usr/sbin/mysqld –basedir=/usr –datadir=/var/lib/mysql –user=mysql –pid-file=/var/run/mysqld/mysqld.pid –socket=/var/run/mysqld/mysqld.sock –port=3306
31941 pts/0 S 0:00 logger -t mysqld -p daemon.error
32292 pts/0 S+ 0:00 grep -i mysql

Moreover I could connect to the localhost SQL server with mysql -u root -p and it seemed to run fine. The error Error establishing a database connection meant that either something is messed up with the database or 192.168.0.2 Mysql port 3306 is not properly accessible.

My first guess was something is wrong due to some firewall rules, so I tried to connect from 192.168.0.1 to 192.168.0.2 with telnet:
 

freebsd# telnet 192.168.0.2 3306
Trying 192.168.0.2…
Connected to jericho.
Escape character is '^]'.
Host 'webserver' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'
Connection closed by foreign host.

Right after the telnet was initiated as I show in the above output the connection was immediately closed with the error:

Host 'webserver' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'Connection closed by foreign host.

In the error 'webserver' is my Apache machine set hostname. The error clearly states the problems with the 'webserver' apache host unable to connect to the SQL database are due to 'many connection errors' and a fix i suggested with mysqladmin flush-hosts

To temporary solve the error and restore my normal connectivity between the Apache and the SQL servers I logged I had to issue on the SQL host:

mysqladmin -u root -p flush-hostsEnter password:

Thogh this temporar fix restored accessibility to the databases and hence the websites errors were resolved, this doesn't guarantee that in the future I wouldn't end up in the same situation and therefore I looked for a permanent fix to the issues once and for all.

The permanent fix consists in changing the default value set for max_connect_error in /etc/mysql/my.cnf, which by default is not too high. Therefore to raise up the variable value, added in my.cnf in conf section [mysqld]:

debian:~# vim /etc/mysql/my.cnf
...
max_connect_errors=4294967295

and afterwards restarted MYSQL:

debian:~# /etc/init.d/mysql restart
Stopping MySQL database server: mysqld.
Starting MySQL database server: mysqld.
Checking for corrupt, not cleanly closed and upgrade needing tables..

To make sure the assigned max_connect_errors=4294967295 is never reached due to Apache to SQL connection errors, I've also added as a cronjob.

debian:~# crontab -u root -e
00 03 * * * mysqladmin flush-hosts

In the cron I have omitted the mysqladmin -u root -p (user/pass) input options because for convenience I have already stored the mysql root password in /root/.my.cnf

Here is how /root/.my.cnf looks like:

debian:~# cat /root/.my.cnf
[client]
user=root
password=a_secret_sql_password

Now hopefully, this would permanently solve SQL's 'failure to accept connections' due to too many connection errors for future.

How road signs evolved / short history of roadsigns

Friday, June 29th, 2012

Reading Time: 2minutes

how the road signs evolved brief history of road signs Ancient Roman Road of Tall Aqibrin

As a person interested in history and antrophology. Just recently on my last trip to Romania as I travelled a very interesting question poped up in my mind – How it happened that RoadSigns we use on every street highway and practically everywhere on the road came to be. Interestingly now with the standartization of road signs often the most popular road signs are used as a basis for development on other popular prohibit or allowance signs, we read on airports public institutions, pubs and mostly everywhere.

So in short I did a short research on Road Sign History, just to find out once again that the ancients, were wiser than we think. The first road signs probably came to existence with the existence of humanity, however officially, there was no standartization of using signs to point on road locations travellers before it was introudced in the Roman Empire. In Rome a pillars on the roads were placed to point to major road arteries leading to Rome and various important empire city centers.

During the middle ages, milestones pillars were no longer used, but for practical reasons wooden markers placed across european cities instructed tradesman and travellers to major city important centers and were used to show a general road direction leading to nearby city.
The wooden signs practice had been in use until the first modern roadsigns erected  on a wide scale designed for riders of 'high' and ordinary bicycles in the late 1870 and 1880s. The modern road signs as we know it today however emerged as a result of the  first International Road Congress meeting that occured in Rome in 1908.
On the meeting a four standard pictures were selected to note the basic for road signs further development. The need for the meeting was the large increase of roads across european artery cities. The road signs developed on the meeting were bump, curve, intersection and railroad crossings. The invention and adoption of cars and the boom of the car producing industry quickened the need for international road sign standard. The intensive work on international road signs that took place between 1926 and 1949 eventually led to the development of the European road sign system as we know it. The signs were quicky spread to America and in 1960, the road signs become universal in America and almost everywhere all around the developed and developing world.

As of today 2012 it can be said road signs exist all around the civilized world.Though most of road signs are identical across all countries around the world today still some road symbols varies from country to country. I remember seeing some very unique road signs during my travelling through Serbia, 2 years ago.
 

How to exclude sorbs.net for a particular IP address in Qmail Mail server install / Fix to Thunderbird mail sent error (Exploitable Server See: http://www.sorbs.net/lookup.shtml?xx.xx.xx.xx) error

Tuesday, November 1st, 2011

Reading Time: 2minutes
In the office, some of my colleagues has started receiving error messages, while trying to send mail with Thunderbird and Outlook Express
The exact error they handed to me reads like this:

An error occured while sending mail. The mail server responded: Exploitable Server See:
http://www.sorbs.net/lookup?xx.xx.xx.xx. Please check the message recipient

Here is also a screenshot, I’ve been sent via Skype with the error poping up on a Thunderbird installed on Windows host.

Typing the url http://www.sorbs.net/lookup?xx.xx.xx.xx lead me to sorbs.net to a page saying that the IP address of the mail client which is trying to send mail is blacklisted . This is not strange at all condireng that many of the office computers are running Windows and periodically get infected with Viruses and Spyware which does sent a number of Unsolicated Mail (SPAM).

The sorbs.net record for the IP seems to be an old one, since at the present time the office network was reported to be clear from malicious SMTP traffic.

The error sorbs.net disallowing the mail clients to send from the office continued for already 3 days, so something had to be done.

We asked the ISP to change the blacklisted IP address of xx.xx.xx.xx , to another one but they said it will take some time and they can’t do it in a good timely matter, hence to make mail sending work again with POP3 and IMAP protocols from the blacklisted IPs I had to set in the Qmail install to not check the xx.xx.xx.xx IP against mail blacklisting databases.

On qmail install disabling an IP check in RBLSMTPD is done through editting /etc/tcp.smtp and following recreate of /etc/tcp.smtp.cdb – red by qmailctl script start.
The exact line I put in the end of /etc/tcp.smtp to disable the RBLSMTPD check is:

xx.xx.xx.xx:allow,RBLSMTPD="",RELAYCLIENT="",QS_SPAMASSASSIN="0"

Further on to recreate /etc/tcp.smtp.cdb and reload the new cdb db records:

qmail:~# qmailctl cdb
qmail:~# qmailctl restart
...

Onwards, the sorbs.net IP blacklist issue was solved and all office computers from xx.xx.xx.xx succeeded in sending mails via SMTP.

How to fix wicd 1.7.0+ds1-5 Connection Failed: Bad Password on Ubuntu 10.10 (Maverick Merkaaat)

Tuesday, May 3rd, 2011

Reading Time: < 1minute
I’ve been struggling with fixing a nasty error with wicd network manager for about 2 hours.
The exact error message I faced was:

Connection Failed: Bad Password

The issue occured after some suggested updates from the Ubuntu graphical update tool.
The wireless network to which it was connected was a WPA-PSK (WPA2) Passphrase authentication.
The network key was properly typed in and was working well on another system so the error Connection Failed: Bad Password made no sense.

There was nothing unusual in /var/log/wicd/wicd.log , that made me even more curious about what might be causing the error.After a lot of try outs and a lot of readings and tests I finally got the cause of the weird Bad Password errors produced by wicd

Weirdly enought, somehow the Ubuntu package update tool has installed the default gnome network-manager package.
The installed network-manager package has mismatched somehow the way wicd connects to wireless networks and as a cause the wpa_supplicant binary was not properly invoked.

As a consequence of the network-manager being present on the system the wpa_supplicant process which made the exact connection to the wireless network was not launching in, the exact wpa_supplicant invocation missing was:

wpa_supplicant -B -i wlan0 -c /var/lib/wicd/configurations/0022b0aa424a -D wext

Luckily the solution to the notebook wireless device unable to connect to the Wireless network was simple.

All I had to do is completely remove all occurance of network-manager packages installed on the Ubuntu system, by issuing the commands:

ubuntu:~# apt-get remove --yes network-manager
ubuntu:~# dpkg --purge network-manager-pptp-gnome network-manager-pptp network-manager

The reason for issuing the a dpkg –purge command was my desire to completely get rid of all kind of network-manager related configurations.

Now after re-connecting with wicd wireless manager, it worked fine 😉