Category: Linux

Create a large file in Linux for testing

There are many ways to go about this.  A common favorite is the use of the dd command. This simple two letter command requires so many parameters to accomplish the simple goal of generating a file of a specific size. There is another way, and it's easier to remember too. Create a 100MB file using dd will look something like...Read More »

Reduce the number of commands with sed

Suppose there is a situation that a server has multiple files that are nearly identical and you want to remove content from them.  In this example suppose that server has multiple NIC cards.  There is content that needs to be deleted. The situation, you have five NIC cards.  Each ifcfg-ethx config file contains the values for NM_CONTROLLED, HWADDR, GATEWAY, and...Read More »

Remove the ^M from config files

Working in both Windows and Linux environments can from time to time create undesirable effects when modifying Linux configuration files on Windows boxes. After the edits and copying the file to the Linux box, a quick check of the file using the cat revealed nothing out of the ordinary.  However, the vim revealed the hidden ^M. I'm still not entirely...Read More »

audit2allow error and explanation.

While troubleshooting some SELinux enforcement related issues using audit2allow, an ERROR message presented itself. After some research, a logical explanation was presented. The following error is an implication that there were no avc denials in the /var/log/uadit/audit.log and that the generated module was empty. That response was satisfactory and also correct for this situation. However, when running an all inclusive...Read More »

Add a new hard disk without rebooting in Linux

Having added a virtual hard drive to a virtual machine, the fdisk -cul command doesn't reveal any new drives.  There are a few ways to get Linux to recognize this new drive without having to reboot the computer. A tried and true method that I have used on many occasions is this approach.  The problem with this approach is that...Read More »

One way to compile xtables-addons without error

There seems to be some consistency on how to compile xtables-addons.  Notice I didn't suggest an agreement in the more popular approaches.  It seems that much of the approach is more of a copy and paste from one site to the next with some slight variation.  What generally isn't immediately obvious is the version of CentOS used or the version...Read More »

How to create a directory with permissions in Linux

The other day I was reading through some newsgroups on how to better automate a script.  Part of the script contained an interesting command that looked promising; however, could not get it work. This is the command. While it looks interesting, a quick execution of it created three directories, icinga:icinga, 0700, and mydirectory. This was not the desired effect. Looking...Read More »

Elasticsearch bootstrap checks failed [RESOLVED]

After installing Elasticsearch the application failed to start with a bootstrap error. The resolution was to modify three files. After logging off, logging back on, the user account successfully started Elasticsearch. Source More »