redhat

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RHEL/CentOS7 create custom cdrom

Posted on by jlim0930

Once in a while you will need to install a system thats not on the network and instead of manually installing it you want it automated with a kickstart file. For most hosts you can create a floppy image with the kickstart file and mount it however on most Dell servers due to the way it handles the device names it can be tricky and this is where a custom cdrom can help. – download the dvd iso – mount the iso.. mkdir dvd; mount -o loop rhel-server-7.2-dvd.iso ./dvd – create a temp directory and copy over the files.. mkdir… Continue Reading →

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use fail2ban to block wordpress login attempts

Posted on by jlim0930

Today while monitoring traffic on my server I noticed that there was 1 IP from UK that is keep accessing my server and generating noticeable amount of traffic. I did a quick IP lookup and netstat to find that the IP was accessing port 80 on my server. I then went to the httpd logs and searched for the IP and wala! it is trying to log into my wordpress site attempt after attempt. Since I already have fail2ban running on my server I decided to look into using fail2ban to ban lots of failed attempts looking at my logs… Continue Reading →

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Linux cleanup before turning images into templates for virtual environments

Posted on by jlim0930

After the OS is installed and prepped there are some cleanup steps needed before turning it into a template. Remove old kernels Remove yum cache Clean out log files Remove device persistencies Clean up MAC and UUID Clean up history and keys I made a sample script that will automate the process. Instead of hosting the script here I’ve moved it to my github.

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all things subscription-manager

Posted on by jlim0930

Register and auto subscribe in one step # subscription-manger register –username –password –auth-attach Register first then attach a subscription in the customer portal # subscription-manger register Attach a subscription from any available that match the system # subscription-manager attach –auth Register with a specific pool # subscription-manager attach –pool= Get pool id # subscription-manager list –available –all Check your enabled subscriptions # subscription-manger list Status of consumed subscriptions # subscription-manager list -consumed Unregister system # subscription-manager remove –all # subscription-manager unregister # subscription-manager clean list all provided repos # subscription-manager repos –list enable/disable repos # subscription-manager repos –enable or –disalbe

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PCI compliance and backporting

Posted on by jlim0930

Due to the complex and sensitive environments of today world many groups of servers will require to get quarterly or annual security audits especially if they are part of PCI. Unfortunately for Sysadmin’s most security scanning tools are blind to backports done by both redhat and novell. backporting is where the security patches are applied to the older (current) versions of the packages that was shipped with a particular version of the operating system. So while you can have 1 major version of the package installed it will have many different versions of backports applied to it. The process itself… Continue Reading →

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VirtualBox – how to create and share disks to setup/test clusters

Posted on by jlim0930

Once in a while you will want to setup clusters with shared disks to test and play around with various clusters. while this is easy to do in kvm/xen/etc its not so easy with virtualbox. There is a way via command line tools to create disks and attaching it so that it is shared. For me I have windows 7 64bit and I am running virtualbox 64bit 4.xxxxx. It is most likely easier if you include the path for “c:Program FilesOracleVirtualBox” however if you do not its ok. We will need to run the command VBoxManage or “c:Program FilesOracleVirtualBoxVBoxManage.exe” if… Continue Reading →