Linux Archives

Over 80% is running on some form of Linux – so does your Mac and you iPhone. Sometimes we have to get our hands dirty on the command line – it makes you feel like a proper hacker.

Here are some pointers I picked up on my journey.

How to fix duplicate packages in yum

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From time to time, the yum package manager may encounter issues with duplicate packages that are erroneously installed on a system. This manifests in a yum update going awry, telling us something along the lines of this:

yum update
...
--> Finished Dependency Resolution
Error: Package: ntp-4.2.6p5-22.el7.centos.2.x86_64 (@updates)
           Requires: ntpdate = 4.2.6p5-22.el7.centos.2
           Removing: ntpdate-4.2.6p5-22.el7.centos.2.x86_64 (@updates)
               ntpdate = 4.2.6p5-22.el7.centos.2
           Updated By: ntpdate-4.2.6p5-25.el7.centos.x86_64 (base)
               ntpdate = 4.2.6p5-25.el7.centos
 You could try using --skip-broken to work around the problem
** Found 41 pre-existing rpmdb problem(s), 'yum check' output follows:
// huge scary list of packages follows

You may at times install all other packages via yum update –skip-broken, but it will still leave some trouble on the system. Best to take care of it.

Here’s how I’ve managed to do it on many occasions:

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How to use variables in a BASH shell script

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Here’s how to use simple variables in BASH shell scripts. It appears there are no data types, and everything’s a string (correct me if I’m wrong). We can define a variable by first setting it to a value, then later refer to that value with a dollar sign in front of the variable name. Here’s … Read more

How to install PHP from source on CentOS

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I have recently installed PHP 7 from source on a fresh minimal CentOS 7 box. No previous version of PHP was installed, and I thought I’d give 7 a spin. There were a few pitfalls I hadn’t come across before, so here’s what worked for me. Downloading and extracting the source code It sounds crazy, … Read more

Upgrade Trouble: when WordPress is asking for FTP details, but there’s no FTP server on your system

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I was working on a CentOS 7 server the other day that had a LAMP stack installed. It was used to host only a single instance of WordPress. Upgrading themes and plugins from the admin interface worked fine, but curiously, WordPress core upgrades did not. Instead, WordPress was asking for FTP details every time, which also … Read more

How to install Python 3 from source in CentOS

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python-logoCentOS 6 comes with Python 2.6 installed, and CentOS 7 comes with Python 2.7. But right now, Python 3.5 is all the rage, so I thought I’d install it alongside Python 2.x on the same machine.

Here’s how I did it.

I’m using a CentOS 6 32 bit system here, but I’ve tried the same on a CentOS 7 64 bit rig. You need to be root or have superuser privileges to do this successfully.

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How to extract tar.xz files on CentOS

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I’ve recently come across a tarsal files that used xz compression (namely the Python source code). This means that my usual way of extracting a tarsal via the command line using the following command did not work: tar -zxvf Python* gzip: stdin: not in gzip format tar: Child returned status 1 tar: Error is not … Read more