First, boot the system with the first Linux CD, when you see boot prompt, type linux rescue to switch to rescue mode. Here, you will be asked if similar steps should be followed, which need to be followed in the installation. At the prompt, type the next command: # chmod /mnt/sysImage # locate grub.conf #… Continue reading GRUB start-up password !
Category: Basics
Authentication token lock busy
This usually happens when you are trying to change a password while the root filesystem (or wherever /etc is) is mounted read-only, for example when you booted up using the init trick, or in some maintenance mode (runlevel, usually). You can mount a filesystem read-write using: mount -o remount,rw / (This can also be useful… Continue reading Authentication token lock busy
Writing Linux firewall rules w/ IPTables
The Linux kernel, since version 2.0, has included the capabilities to act as a firewall. In those days, the kernel module was called ipfwadm and was very simple. With the 2.2 kernel, the firewall module became called ipchains and had greater capabilities than its predecessor. Today, we have IPTables, the firewall module in the kernel… Continue reading Writing Linux firewall rules w/ IPTables
DNS Cache Poisoning Test
Q. How do I verify that my ISP or my own recursive resolvers are free from DNS cache poisoning bug that is promised full disclosure of the flaw by Dan on August 7 at the Black Hat conference? How do I test my dns server for DNS cache pollution or DNS Cache Poisoning bug? A.… Continue reading DNS Cache Poisoning Test
hwclock – query and set the hardware clock
set the system time from the hardware clock ============================================ root@s1 [~]# /sbin/hwclock –hctosys root@s1 [~]# set the hardware clock to the current system time ============================================ root@s1 [~]# /sbin/hwclock –systohc root@s1 [~]# root@s1 [~]# /sbin/hwclock –help hwclock – query and set the hardware clock (RTC) Usage: hwclock [function] [options…] Functions: –help show this help –show read… Continue reading hwclock – query and set the hardware clock
error: stat of /var/log/cron failed: No such file or directory
Hi guys… Today I faced a issue with a new VPS installed with EZ template Centos 5.2. I was preparing the VPS with logwatch, apf and other security and got cron error under roots mail. Cron errors shows log errors : /etc/cron.daily/logrotate: error: stat of /var/log/boot.log failed: No such file or directory error: stat of… Continue reading error: stat of /var/log/cron failed: No such file or directory
cPanel / APF – Passive FTP issue
The following web site will redirect you to a very well written article, which will cover the basics of “Passive vs Active” mode functions. Active FTP vs. Passive FTP, a Definitive Explanation After FTP connection has been made, The FTP server will generally choose a random port within a certain range to use and tell the… Continue reading cPanel / APF – Passive FTP issue
Linux Memory Management
Scenario: Customer is concerned that only 100MB of their 2GB of memory is as unused or free when running the free command. However, no processes appear to be consuming large amounts of memory, and the server is not running slow. Cause: This is not a problem, but rather a result of the way linux manages… Continue reading Linux Memory Management
Performance tuning tools: ps, top, sar, iostat, and vmstat
Performance tuning tools :by Matt Frye P.S.—I want to see my processes Being on top Sar, yes, sar! Check your system, STAT! About the author As a system administrator, part of your daily duties is to monitor systems for performance and to tune systems where necessary. While there are expensive software products and benchmarking tools… Continue reading Performance tuning tools: ps, top, sar, iostat, and vmstat
Hotlink protection: How-To prevent people from stealing your files
Create an .htaccess file in your public_html directory with the following code: RewriteEngine on RewriteCond %{HTTP_REFERER} !^$ RewriteCond %{HTTP_REFERER} !^http://(www.)?domain.com.*$ [NC] RewriteRule .(gif|jpg)$ – [F] Where domain.com is your domain.