The operation, reliability, and performance of your servers is in large part determined by the operating system running on the server. One of the most universally used operating systems for servers is CentOS. It has great features and performance, it’s a very stable system, and it’s backed by enterprise-focused institutions such as Red Hat and Fedora.
The first CentOS release was in May 2004 and most servers out there are running CentOS 6 or CentOS 7. CentOS 6 is actually approaching end-of-life, and server administrators everywhere need to upgrade to CentOS 7.0 to have a more functional and reliable server. The stated deadline after which CentOS 6 will no longer receive updates is November 30th, 2020.
All CanSpace servers are running CentOS 7, so we are prepared for the phaseout of version 6. But is your host doing the same? Most hosting providers are still running CentOS 6, as the upgrade process is a fairly major endeavour. cPanel will also stop supporting CentOS 6 in November 2020, meaning at that time your site may be vulnerable as they will stop providing updates and security patches.
Choosing a hosting provider that stays on top of these things, and makes regular updates to their systems, is imperative to have a stable, and secure website.
CentOS 7.0 improvements over CentoOS 6 include:
- Kernel updated to 3.10.0
- Support for Linux Containers
- Open VMware Tools and 3D graphics drivers out of the box
- OpenJDK-7 as default JDK
- In Place Upgrade from 6.5 to 7.0 (as already mentioned)
- LVM-snapshots with ext4 and XFS
- Switch to systemd, firewalld and GRUB2
- XFS as default file system
- iSCSI and FCoE in kernel space
- Support for PTPv2
- Support for 40G Ethernet Cards
- Supports installations in UEFI Secure Boot mode on compatible hardware
There is also a list of known issues, which those moving to CentOS 7 should be aware of:
- Many people have complained that Ethernet interfaces are not started with the new default NetworkManager tool/have to be explicitly enabled during installation. See CentOS-7 FAQ#2.
- The installer needs at least 406MB of memory to work. On systems with less memory then 406MB the installation will terminate with a fatal error. 512MB is the minimum memory requirement for CentOS-7.
- Installing CentOS-7 to a VirtualBox virtual machine in UEFI mode on an encrypted file system does not work properly. The installed system will not show the prompt for the volume passphrase, unless the kernel command line is modified. See the bug report for more details.
- If your screen resolution is 800×600 or lower, parts of the images shown at the bottom during install are clipped.
- The EULA file in the root directory of the .iso images has an incorrect statement saying these images should only be used for testing. The correct updated EULA can be found from /usr/share/centos-release/EULA on the installed system.
- VMware Workstation/VMware ESXi allow to install two different virtual SCSI adapters: BusLogic and LsiLogic. However the default kernel from CentOS-7 does not include the corresponding driver for any of them thus resulting in an unbootable system if you install on a SCSI disk using the defaults for CentOS Linux. If you select ‘Red Hat Enterprise Linux’ as OS, the paravirtualized SCSI adapter is used, which works.
- Commonly used utilities such as ifconfig/netstat have been marked as deprecated for some considerable time and the ‘net-tools’ package is no longer part of the @core group so will not be installed by default. Use nmcli c up ifname $interface to get your network up and running and use yum to install the package if you really need it. Kickstart users can pull in the net-tools package as part of the install.
- The AlpsPS/2 ‘ALPS DualPoint TouchPad’ edge scrolling does not work by default on CentOS-7. See bug 7403 for the command to make this feature work.
- In VirtualBox up to version 4.3.12 the building of the vBox additions fails. This is solved starting with version 4.3.14. On Windows hosts there still seem to be some issues with versions up to 4.3.16. After installing vBox additions logging in to GNOME Desktop results in a black screen or a terminating VM.
If you’re moving from CentOS 6, you’ll definitely want to use a test environment to see if your current systems can run safely on CentOS 7. There are numerous changes to the underlying OS, command syntax, and even package versions available.
Have questions about switching your server to CentOS 7? Reach out to us!