How to change maximum sync speed of linux software raid
After few unsuccesfull google searches about changing linux software raid sync speed (while waiting for idle CentOS to sync 3×200Gb SATA raid1) I decided to run: ffind /proc/ -name \*raid\* which lead...
View ArticleHow to force setuid program to make core dump
If you want to debug why your C/C++ application segfaults once in a while (daemon that segfaults once in few days) under Linux the obvious way is to tell your program to create core dump files on...
View ArticleHow to make site screenshots with linux server
Ever wanted to be able to create site screenshots, just like alexa? Want to do it on your server with a script? Than read this article. The idea is simple: install xvnc on your server, so you’ll have...
View ArticleUsing O_LARGEFILE or O_DIRECT on Linux
Today after some backups, generated from my C program generated few files exactly 2Gb in size I’ve remembered that there was some parameter to open for working with large files. I’ve opened man page...
View ArticleHow to restore reiserfs partition from crashed disk
Few days ago, a server of mine had all of it’s 4 disk crashed. The problem was that one of the disks was overheating and that seemed to help other harddrives to crash (don’t buy Maxtor). So, if you...
View ArticlePHP forms spam
There are many forms on the web, that use PHP mail() function to send mail, most of the time to the site owner. The problem with this is that many of them do not verify submitted data and can be used...
View ArticleHow to check if a hostname is a valid registered nameserver
If you need to check for instance if “ns1.titov.net” is a registered nameserver and can be filled as nameserver for a domain you can do it this way: ask which nameservers are authoritative for zone...
View Article“Do not use ORDER BY RAND()” or “How to get random rows from table?”
Quite often people use queries like: SELECT quote FROM quotes ORDER BY RAND() LIMIT 1 to get a random row (rows) from a table. That’s quite bad idea. For big tables, if your table have just 50-100...
View ArticleFront page extensions without mod_frontpage
If you have apache server on linux and want to be able to activate front page extensions for virtual hosts but do not want to install mod_frontpage, than you can download this file...
View ArticleDate and time addition and substraction
Real life example: SELECT username FROM users WHERE (ADDDATE( last_in_chat, INTERVAL 2 MINUTE) > NOW()) ORDER BY username LIMIT 30 NEVER do that. The user in question runs this query on table with...
View ArticleTraffic accounting and IP restrictions on linux bridge
These days I’ve implemeted a Linux bridge that does traffic accounting and IP restrictions per mac adress and decided to share my experience. In my setup on eth0 is my gateway and on eth1 is switch...
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