Category Archives: linux

Compiling Latest Linux Kernel

TweetHi Friends, As per requirement of our client, recently I compiled latest stable Linux kernel (linux-3.9.7) on my CentOS-6.3. So as usual I wanna share steps for compiling the kernel 🙂 Below are the steps. Please follow if you also want to do the same. Step 1) Download latest stable Linux Kernel from and untar the… Read More »

>How Linux Store Password

Tweet> In Linux, user information stored inside /etc/passwd and password in /etc/shadow. In this post, I will discuss password storage in Redhat Enterprise Linux 5.x. On a Linux system where there is a user with name vishesh exist, the entry in /etc/shadow is as below vishesh:$1$QcuAEvix$zeCS9ESc4ch7Xl4CVTlbGC/z.DQKhPjdSzDAstNH5USxakhMyQnhv2IU6fki9qzxHvroh2Rr372GorD1cPCc5.:15866:0:99999:7::: 2nd column of above given line is the password, note that… Read More »

> Authentication module /lib/security/ is missing

Tweet> Recently, On one of my CentOS6 server I executed the authconfig-tui command and select  “Use Kerberos” in Authentication part On clicking on Next button and then setting up, REALM, KDC and Admin On clicking on ok button, I got following error “Authentication module /lib/security/ is missing. Authentication process might not work correctly.” So what… Read More »

>Limit su access to certain users only

Tweet> In the series of my articles on Linux Security , Today I am going to discuss “How to Limit su access to certain users only “ We all know that any user can do su to gain access to root user . We also know that doing su ask for root password , but… Read More »

>Setup Internet Connection On Linux

Tweet> These days cheap internet options are available in the market . Linux support all of the internet connectivity options without any issue . You can choose from  wire ,wireless or whatever option suit you . Some people think that configuring Internet on Linux platform is a bit complicated task, but that’s not true. Here… Read More »


Tweet> Friends last few days were so busy days for most of my seniors. Actually one of our client has deleted (accidently) some important configuration files from server. We did lot’s of troubleshooting to make server up. On those trouble shootings I got opportunity to learn some precious things. For me it was like practical… Read More »

>log-rotate in Linux

Tweet> Today my client claimed to reset the log rotation of access_log to 1 day and 1 log of all his 532 websites hosted in a server . Also he claimed that all rotated log will be mailed to him . Then I did :-> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Step 1:-> create a file # vi logger.conf /var/www/vhosts/*/statistics/logs/access_log… Read More »

>Logging Bind Queries

Tweet> To log DNS  queries on linux, we use logging feature of Bind server.Suppose you want to log dns queries in file /var/log/querylog.log in this case make following entries in /etc/named.conf.   logging {              channel querylog{                                â€¦ Read More »

>Authentication in single user mode

Tweet> After a long time i am here with an security trick. Many occasion we need to move into single user mode , which is very simple. But this can be security risk also to overcome this either we can use password in grub boot loader or we can go with following simple solution —————————————————… Read More »

>Extended Globbing

Tweet> As we know Wildcard in bash refer as pathname expansion and also as globbing. The use of * , ? etc in command parameter it represent something. For example following command    root#echo * What you guessing? It should print * , but no it will not print * but instead it will list you… Read More »