Saturday, November 29, 2014

No Space in /boot and Removing Old Kernels

A practice that Linux distributions recommends is to put Linux kernel images in a separate partition that is mounted at /boot. It is a common problem that the /boot partition becomes full, which prevent any new kernel images from being installed to copied to the partition. To resolve this problem, there are commonly two solutions.
  • Solution 1. Increasing the size of the /boot partition.
  • Solution 2. Removing old kernel images from the /boot partition.
This post discusses Solution 2. Previously I took a note how we may remove old kernel images and packages from Ubuntu Linux (or any Debian-based Linux distributions). In this post, I would like to take a note on removing old kernel images and packages from Fedora Linux (or any Redhat Linux-based systems). I have been used two methods that lead to the same results. I would recommend the second method for simplicity. However, if you want to know what packages and images are removed, you may want to use the first method.
  • Using rpm.
    1. First determine what Linux kernel images are present in the /boot partition.
      
             $ ls /boot/vmlinu*
             /boot/vmlinuz-3.14.23-100.fc19.x86_64
             /boot/vmlinuz-3.17.3-200.fc20.x86_64
             

      The above shows that we have two Linux kernels present in the /boot partition. Now we want to make room in the /boot partition. Once we make sure that we can boot from the /boot/vmlinuz-3.17.3-200.fc20.x86_64, we can remove the old kernel image and associated kernel package.
    2. We now find out what packages that we need to uninstall to remove the old kernel package, in this case, /boot/vmlinuz-3.14.23-100.fc19.x86_64.
      
             $ rpm -qa | grep 3.14.23
             kernel-devel-3.14.23-100.fc19.x86_64
             kernel-3.14.23-100.fc19.x86_64
             
    3. From the above, we can now remove the two packages.
      
             $ sudo rpm -evh \
                    kernel-devel-3.14.23-100.fc19.x86_64 \
                    kernel-3.14.23-100.fc19.x86_64
             

      Alternatively, we can also use yum to remove the two packages.
      
             sudo yum remove \
                    kernel-devel-3.14.23-100.fc19.x86_64 \
                    kernel-3.14.23-100.fc19.x86_64
             
  • Using the yum-utils package.
    1. We first install the yum-utils package.
      
              sudo yum install yum-utils
              
    2. The yum-utils package has a tool called package-cleanup. We now use it to remove old kernel images and associated packages, which is done by specifying the number of kernel images that we would like to keep in the system. In this example, we would like to keep only one kernel image. Then, we issue the following command,
      
              sudo package-cleanup --oldkernels --count=1
              
    I learned the method of using yum-utils from a web post here, which also discusses how you may configure the system to always keep a given number of kernel images and associated packages.

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