Linux For You Mate ...

"dd" Command is used to monitor write performance of a disk on the Linux OS. Typical DD syntex: dd if=/dev/<input_file> of=/path/to/<output_file bs=<block-size> count=<number-of-blocks> <other_options> Use the dd command to : 1. Measure server throughput (write speed) dd if=/dev/zero of=/tmp/out-file1.img bs=1G count=1 oflag=dsync Note: "oflag=dsync" option means use synchronized I/O for data. It doesn't use cache and gives accurate results 2. Measure server latency dd if=/dev/zero of=/tmp/out-file1.img bs=512 count=1000 oflag=dsync If you want to run RAW IO on a disk directly for long time you can run dd command in while loop loop; # while true;do dd if=/dev/zero of=/dev/sdb bs=2048 count=5000 oflag=dsync;sync;done; To come out of this loop use "Ctrl + C".

Here are some of the tricks, i'll keep it updating as i'll get something new. Cheers :) 1 . use "ftp 0" or "ssh 0" command instead of typing "ftp 0.0.0.0" or "ssh localhost" or "ftp localhost" for quickly testing newly configured ftpd or sshd service. 2 . See memory and rss usage on your system: #watch ps -A --sort -rss -o pid,comm,pmem,rss 3 . Sample random password generator (put in your ~/.bashrc): genpasswd ( ) { local l= $1 [ "$l" == "" ] && l= 20 tr - dc A-Za-z0-9_ < /dev/urandom | head -c $ { l } | xargs } Run it: genpasswd 16 Output: uw8CnDVMwC6vOKgW 4. You can configure any Linux system to automatically log users out after a period of inactivity. Simply login as the root user and create a file called /etc/profile.d/autologout.sh, # vi /etc/profile.d/autologout.sh Append the following code: TMOUT= 300 readonly TMOUT export T...

Many of admins are depend on Putty to record SSH session on a file, but what if you want do it without Putty in to Linux console? What if you want to show live SSH session with recording to someone else while he's also logged to same remote session? Here is the solution :) Use below command while connecting to remote host e.g. "10.20.30.40"; # ssh jerry@10.20.30.40 | tee -a ~/jerry_ssh_file.txt Now either you can see this recorded session later with below command; # cat ~/jerry_ssh_file.txt Or to see it like live session on another remote SSH console or on another terminal use; # tail -f ~/jerry_ssh_file.txt

Normally you will need Oracle essential packages for Oracle 11gR2 Database and RAC installation & configuration. #cd /etc/yum.repos.d #wget http://public-yum.oracle.com/public-yum-ol6.repo #yum list #yum install oracle-rdbms-server-11gR2-preinstall =============== For Other OS's: =============== Download and copy the appropriate yum configuration file in place, by running the following commands as root: Oracle Linux 4, Update 6 or Newer # cd /etc/yum.repos.d # mv Oracle-Base.repo Oracle-Base.repo.disabled # wget http://public-yum.oracle.com/public-yum-el4.repo Oracle Linux 5 # cd /etc/yum.repos.d # wget http://public-yum.oracle.com/public-yum-el5.repo Oracle Linux 6 # cd /etc/yum.repos.d # wget http://public-yum.oracle.com/public-yum-ol6.repo Oracle VM 2 # cd /etc/yum.repos.d # wget http://public-yum.oracle.com/public-yum-ovm2.repo Enable the appropriate repository by editing the yum configuration file     Open the yum configurat...

To do it, first you need to collect below two details; FTP / HTTP YUM server IP i.e. "10.0.0.1" Packages location on remote YUM server i.e. "/rhel6_64repo/Packages/" Then create a repo file " rhel6_ftp_remote " in "/etc/yum.repos.d/" folder with below content; [rhel6_ftp_remote] name=Remote FTP Repository for RHEL6 $releasever – $basearch baseurl= ftp ://10.0.0.1/rhel6_64repo/Packages/ enabled=1 gpgcheck=0 If you want to add HTTP repo link, then replace "ftp" with "http". [rhel6_http_remote] name=Remote HTTP Repository for RHEL6 $releasever – $basearch baseurl= http ://10.0.0.1/rhel6_64repo/Packages/ enabled=1 gpgcheck=0 To add Local repo, read this article .

How to setup local yum repository on RHEL or CentOS 7?  This tutorial describes how to setup a local Yum repository on CentOS or RHEL 7 system. Later i will show you how you can use this repository to fetch software, security updates and fixes. Local repository is an efficient way to deploy new software's or patches as it will be over LAN where deployment will be fast, saving your internet bill. I have two CentOS 7 systems here one is YUM repository server and another will be Client which will fetch the updates from repository server over FTP protocol. Setting up YUM repo server with FTP: Step 1. Mount CentOS 7 ISO and copy all the RPM packages to a FTP directory: [root@localhost ~]# mount /dev/cdrom /mnt/ mount: /dev/sr0 is write-protected, mounting read-only [root@localhost ~]# mkdir /var/ftp/pub/localrepo [root@localhost ~]# cp -ar /mnt/Packages/* /var/ftp/pub/localrepo/ Step 2. Install vsftpd package and start it's service: [root@localhost ~]# cd /mn...

The Linux kernel allows drivers and features to be compiled as modules rather than as part of the kernel itself. This means that users can often change features in the kernel or add drivers without recompiling, and that the Linux kernel doesn't have to carry a lot of unnecessary baggage. Want to learn how to manage your modules? It's easy to do, just keep reading. In this tutorial, we'll walk through the steps of seeing what's already loaded in the running kernel, and adding and removing modules from the kernel. What's Loaded 1. To see Loaded Kernel driver or module information for PCI components: [root@localhost ~]# lspci -k 00:00.0 Host bridge: Intel Corporation 440BX/ZX/DX - 82443BX/ZX/DX Host bridge (rev 01)         Subsystem: VMware Virtual Machine Chipset         Kernel driver in use: agpgart-intel 00:01.0 PCI bridge: Intel Corporation 440BX/ZX/DX - 82443BX/ZX/DX AGP bridge (rev 01) 00:07.0 ISA bridge: Intel Corporation 82371...