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The rock-dkms loadable kernel modules should be installed using a single rock-dkms package. ROCm v3.9 and above will not set any ldconfig entries for ROCm libraries for multi-version installation. Users must set LDLIBRARYPATH to load the ROCm library version of choice. NOTE: The single version installation of the ROCm stack remains the same.The rocm-dkms package can be used for single. That last link about compiling nVidia drivers with dkms is utterly unhelpful and completely irrelevant. To resolve this issue: 1. Add the Extra Packages for Enterprise Linux (EPEL) repository to your system (I'm presuming you're running CentOS 7.x or RHEL 7.x).

1. Install Virtualbox 6.1 On Centos 7
2. Installing Dkms On Centos 7 Virtualbox

Developed by Sun Microsystems, later acquired by Oracle Corporation, ZFS is one of the most popular storage systems today. It was created by combining the file system and Logical Volume Manager (LVM). ZFS comes with some great enterprise-level features such as data compression, copy-on-writes, data redundancy, snapshots, error checking and many more.

ZFS was fully open source during Sun Microsystems but after acquiring Sun, Oracle reverted ZFS to closed source. In response, OpenZFS was born in 2013 to bring individual developer and companies together to continue maintaining ZFS in an open source manner. ZFS is not enabled by default in CentOS 7. In this guide, we are going to learn how to configure ZFS on CentOS 7.4 and above.

Step 1: Add ZFS Repository

First, we need to check which version of CentOS is currently installed using the following command:

After the CentOS version is verified, we can add the repo of ZFSOnLinux using the following command:

Step 2: DKMS vs kABI

DKMS and kABI are two ways ZFS module can be loaded into the kernel. If DKMS is used then if CentOS kernel is ever updated, the ZFS module will need to be recompiled again. But with kABI no recompilation is necessary. In this guide, we are going to use kABI. We can enable it by editing the ZFS repository:

The following content should be in the repository file where [zfs] is for DKMS and [zfs-kmod] is for kABI. We can see that the DKMS is enabled by default and kABI is disabled:

We are going to disable DKMS and enable kABI by editing the enable= in both sections as following:

Step 3: Installing ZFS

With repository fully configured, we are now ready to install ZFS using the following command:

Reboot the computer to activate ZFS so modules can be loaded:

Step 4: Check ZFS Kernel Module

After rebooting is done, use the following command to check if the ZFS kernel module is loaded automatically:

If the module is loaded properly, we should see it as follows:

If for some reason the module is not loaded, we can manually load it using the following command and check again:

Step 5: Creating ZFS Pool

A ZFS pool combines drives together to perform single storage. Pools should always be created on disks which are currently not in use. So when the storage needs to be expanded simply add drives to the pool to increase overall storage capacity. This offers to scale without restriction.

Step 5a: Pool Naming Convention

ZFS pool and dataset name must follow the strict naming convention:

• The name can only contain alphanumeric characters including the following four special characters:
  • Hyphen -
  • Underscore _
  • Colon ;
  • Period .
• The name must begin with a letter with the following exceptions:
  • Reserved names cannot be used: log, mirror, raidz, raidz1, raidz2, raidz3, spare.
  • Name must not contain percent (%) symbol.
  • The naming sequence must never be as c[0-9].

There are three types of pools that can be created in ZFS:

• Stripped Pool
• Mirrored Pool
• Raid Pool

Each offers its own sets of advantages and disadvantages. It is important to decide which type of pool is going to be used. Because once the pool is created it cannot be undone. In order to change pool, a new pool would need to be created, then migrate all data from the old pool to the new pool then delete the old pool.

Step 5b: Creating Striped Pool

This is the basis ZFS storage pool where incoming data is dynamically striped across all disks in the pool. Although this offers maximum write performance, it also comes with a price. Any single failed drive will make the pool completely unusable and data loss will occur. Besides the performance, the biggest advantage of Stripped pool is total storage capacity is equal to the total size of all disks. We can use the following command to create a ZFS Striped pool:

To increase the size of the striped pool, we can simply add a drive using the following command:

It is important to note here that, when a new disk is added to a striped pool, ZFS will not redistribute existing data over to the new disk, but will favour the newly added disk for new incoming data. The only way to redistribute existing data is to delete, then recopy the data in which case data will be stripped on all disks.

Step 5c: Creating Mirrored Pool

As the name suggests, this pool is consists of mirrored disks. There are no restrictions on how the mirror can be formed. The main caveat using the mirrored pool is we lose 50% of total disk capacity due to the mirror.

To create a mirror pool of just two disks:

To expand a mirror pool we simply need to add another group of the mirrored disk:

When adding another mirror group, data is striped on to the new mirrored group of the disk. Although it is rare, it is also possible to create a mirror of more than two disks:

Step 5d: Creating Raid-Z1, Raid-Z2 or Raid-Z3 Pool

ZFS offers software-defined RAID pools for disk redundancy. Since it is not depended on hardware RAID, all disks of a pool can be easily relocated to another server during a server failure. All Raid-ZX in ZFS works similarly with the difference in disks tolerance. The main difference between Raid-Z1, Raid-Z2 and Raid-Z3 are they can tolerate a maximum of 1, 2 and 3 disk failure respectively without any data loss.

To create Raid-Z1 we need a minimum of two drives:

To create Raid-Z2 we need a minimum of 3 drives:

To create Raid-Z3 we need a minimum of 4 drives:

When using any raidzX pool, it is important to keep in mind that, a disk loss puts the pool under heavy load due to data rebalancing. The bigger the pool, the longer it will take for rebalancing to complete.

Once a Raid-ZX pool is created it cannot be expanded just by adding new disk to it. In order to expand the pool we need to add another complete vdev. A vdev is a complete group of disks which can be standalone forming a pool or multiple vdevs forming a pool. For example, a Raid-Z3 consisting of 4 drives is one vdev. To expand the pool we need to another vdev of mirror, Raid-Z1, Raid-Z2 or Raid-Z3 vdev. Following command is to expand a Raid-Z3 with another Raid-Z3 vdev:

Step 6: Adding Cache/Log Disk

We can increase both read and write performance significantly by adding faster disks such as SSD or NVMe. Cache disks increased read performance while Log disks increases write performance. These disks can be added during pool creation or even after the pool has been created. The cache and log disks can also be mirrored to increase performance redundancy.

To add mirror Cache disks during pool creation to increase read performance:

Note that it may take a while to achieve maximum read performance because ZFS will automatically copy most frequently accessed data to the Cache disk over time.

To add mirror Log disks during pool creation to increase write performance:

Common ZFS Commands

To check pool status:

To see list of ZFS datasets

To import a ZFS pool which was created on another server:

DKMS:
– Dynamic Kernel Module Support (DKMS) is a framework used to generate Linuxkernel modules whose sources do not generally reside in the Linux kernelsource tree. DKMS enables kerneldevice drivers to be automatically rebuilt when a new kernel is installed.
– An essential feature of DKMS is that it automatically recompiles all DKMS modules if a new kernel version is installed. This allows drivers and devices outside of the mainline kernel to continue working after a Linux kernel upgrade.
– Another benefit of DKMS is that it allows the installation of a new driver on an existing system, running an arbitrary kernel version, without any need for manual compilation or precompiled packages provided by the vendor.
– DKMS was written by the Linux Engineering Team at Dell in 2003. It is included in many distributions, such as Ubuntu, Debian, Fedora, and SuSE. DKMS is free software released under the terms of the GNU General Public License (GPL) v2 or later.
– DKMS supports both the RPM and DEB package formats out-of-the-box. (from Wikipedia)
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I was trying to install guest additions on my Centos operating system but faced a lot of problems. Though the idea was very simple as all you have to do was to install DKMS package on your centos operating system and run the install virtual box guest additions setup, but the main problem is that dkms package is not available on your centos, it is a third party repository. So I believe there are a lot of new users who face this issue (I being one of them).

Following steps will help in installing guest additions on your centos.

Step1: update everything( though not really required but still I took this step 1st)

Step2: make a directory rpm using the following commands and go in that directory and download the rpm package from this link or goto http://pkgs.repoforge.org/rpmforge-release/ and download the appropriate package.

Install Virtualbox 6.1 On Centos 7

now if you get an error something like this

That means you have installed your centos virtual machine from cloudera which is centos5 and you have downloaded rpm package for centos6 so all you have to do is to change that package and download package for centos5. You can also check if you are running a 32 bit machine or a 64 bit machine as there are two packages one is for 32 bit machine and the other for 64 bit. To check which machine you are running just type the following command

if you get i386 or i686 that means you are running 32 bit machine and if you get x86_64 that means you are running a 64 bit machine.

Step3. Install kernel-devel

Step4. So almost everything is done and you are ready to install dkms package

if everything goes fine dkms package will install successfully, without any issues.

Step5. This will be the final step

Insert VboxGuestAdditions.iso and go to the folder which will be probably in

/media/VboxGuestAdditions

and run the following command

This will successfully install Guest Additions on Centos.

Installing Dkms On Centos 7 Virtualbox

By: Saad