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Tag: server (Page 3 of 8)

Fixed a strange network problem

I have three routers in house. One is provided by ISP, Telus. It is 2 in 1, including modem and router. The second router is Buffalo WZR-HP-G300NH. It is placed beside Telus device. There two are connected with lan cable. Both are in the living room ground floor. The third router is located at basement. It is Buffalo WZR0HP-G300NH2. It is connected to the second router with wireless connection as client bridged.
I drew a reference layout.
network-layout

Now, let me describe the network problem. It bothered me for two months.
I have a PC, Windows 7, in the basement, connect the router 3 with wire connection.
Normally I have no problem to working on this PC. Web browsing, online gaming, streaming video.
Until last month, I tried to install a Centos server. The server can not do update, can not wget remote files.
In the server terminal window, I can ping domain and get the IP address of Google.com, but I can not traceroute path to Google.com. It said network is unreachable, something like that.
When I tracert my host from Windows, the error looks like below:
tracert-error

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Solved MySQL 5 – Incorrect integer value: ” for column ‘id’ at row 1

I move one site to a new server with Windows 2003.
It is a MySQL database. I use PHP script to connect the database file and query it.
I run the same script more than 5 years on the old server. After I move it to new one, it gives me the error as subject.
I did a lot of Googling. Found the answer at this blog(the link is not working any more), but now it is not available. So, I quoted the most important part from the Google Cached page.

This is an sql-mode issue, the mode defines what SQL syntax should be supported and what kind of data validation should be performed. In my problem MySQL is trying to assign an empty string to an auto-increment INT field and, as we should all know, strings into INTs don’t go. Cue errors and the script dies.
Longer term I am going to have to re-work my code to fix this issue, but in the short term, I am going to reduce the sensitivity of the control. To lower the level of data validation we can set the sql-mode to a lower level or comment it out altogether.

Solution is below:
Edit the my.cnf (my.ini in windows) file and find and comment out the line:
#sql-mode=”STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION”

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OpenSSH server Security Top 6

OpenSSH is very popular SSH server. Widely used on different Linux distribution. I used it for many years on my VPS server. It is easy to use, but security is the top issue for any server. Here is the top 6 security settings for Open SSH server.

To make it safe and minimize the risk, change the default setting and make it more safe.
OpenSSH setting file is located:

/etc/ssh/sshd_config

1) Only Use SSH Protocol 2
SSH protocol version 1 (SSH-1) has man-in-the-middle attacks problems and security vulnerabilities. SSH-1 is obsolete and should be avoided at all cost. Open sshd_config file and make sure the following line exists:

Protocol 2

2) Allow Only Specific Users or Groups (AllowUsers AllowGroups)
By default anybody who is authenticated successfully are allowed to login. Instead you can restrict which users (or groups) you allow to login to the system.

This is helpful when you have created several user accounts on the system, but want only few of them to login.

This is also helpful when you are using NIS, openLDAP (or some other external system) for authentication. Every user in your company might have account on NIS, OpenLDAP etc. But, on a specific server you want only few of them to login. For example, on production system you want only sysadmins to login.

Add the following entry to the sshd_config file to allow only specific users to login to the system. In the example below only ramesh, john and jason can login to this system. Usernames should be separated by space.

AllowUsers ramesh john jason

Add the following entry to the sshd_config file to allow only the users who belong to a specific group to login. In the exampe below only users who belong to sysadmin and dba group can login to the system.

AllowGroups sysadmin dba

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Video card driver makes Windows 2008 R2 Blue Screen

Yes, it is true. I have see so many blue screens on a brand new PC server with Windows 2008 Server R2.
The hardware including following items:
Intel i5 2500 CPU
1TB SATA2 Hard Disk
ASUS P8P67 R3 mother board
Corsair DDR3 Memory 4GBX2
ASUS HD5450 512M Video card.
etc.
I installed Windows Server 2008 R2 on it. 64bit OS is my choice.
After few days running, it has blue screen randomly. Sometimes it happened 4 days up. Sometimes it is 10 days up.
It is not predicted.
Blue Screen error code is as blow:
STOP:0x0000000A
or
STOP:0x0000003B
I tried update Intel Chip set driver, update BIOS of mother board. Change SATA cable, chage SATA port.
Still has this kind of error when Blue Screen.

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Amazon extend Edge Locations in Paris

Got the newsletter from Amazon.

We’re excited to inform you about the addition of a new edge location in Paris, France to serve end users of Amazon CloudFront and Amazon Route 53. With this new location, CloudFront and Route 53 now have a total of 5 edge locations in Europe, and 18 total edge locations worldwide. Each new edge location helps lower latency and improves performance for your end users in that region. We plan to continue to add new edge locations worldwide throughout 2011.

It is a good news. I use Amazon CloudFront as a cache system, or CDN, on many sites. It always give a good performance from USA, Canada, etc. Now It has more and more edge locations around the world. So every one can get the content from the closer server.
Yes, this blog is also powered by Amazon FrontCloud.

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Cancel Swvps service

Because of the service is not stable any more, to protect my sites and save the traffic, I have to move all my sites from Swvps to other VPS.
I said, I give up it.
So I submit the cancellation request ticket to Swvps. Ask for canceling my VPS at the end of billing cycle.
Now I recommend Burst.net VPS service. I have a busy forum on it.

Amazon CloudFront support custom origin

Amazon just announced that CloudFront now support custom origin, which means users can use their own server as the original content storage. You don’t have to use S3 as origin.
It is more flexible for users. Easy to integrated with CMS system.
Her are some reference of custom origin.
Defination of Origin Server.
Developer Guide: Appendix Custom Origin
Right now, AWS management can not create CloudFront with custom origin. But, if you have a distribute with custom origin, you can manage it in AWS management.

Google mod_pagespeed make Centos crush

I am not sure, what is the problem. When I install the mod_pagespeed on my Centos VPS, it make the Apache crushed. It ate a lot of memory, until over the memory limit. I have to restart the VPS.
Just a few minutes, it happened again.
So I have to remove it and use my manual optimize. Actually, Google mod_pagespeed does not make my web page faster. Same pagespeed score. Same YSlow score.

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