Red Hat Enterprise Linux 7 (RHEL / RHEL 7 / RHEL7) and CentOS 7 have quite a few changes in store for those used to the way things have been done for a very long time in the Fedora/CentOS/RHEL Linux world. Note, except where otherwise stated, information related to RHEL7 in this article applies more or less directly to CentOS7 as well.
Issue #1. Ethernet Devices are not auto-started after Install
The biggest initial shock to the system is that RHEL7 treats wired network devices a lot more like Wireless networks have been traditionally used. By default, it won’t auto-start the devices after install, which is very much antagonistic to the “Principle of Least Surprise” way it has been done.
Issue #2. Ethernet devices don’t use “eth0″..”ethX” naming by default
This change is coupled with an effort to provide a more-consistent device naming for network devices under RHEL7. This means that, by default, you won’t see an “eth0” in RHEL7. Instead, you’ll see device-names like (in the case of VMWware ESXi 5.x): “ens192”.
Issue #3. The command-line utilities used to configure the network have changed
Oh, and they also removed ‘ifconfig’ from the default ‘Minimal Install’ of the OS. This can make for a pretty jarring experience all-tolled.
Here are a list of things that can be done with regard to those issues:
To fix Issue #1:
During install, When the “Installation Summary” screen appears:
- Click on the “Network & HostName” section.
- The “Network & HostName” section screen will appear.
- Verify that an Ethernet device shows on the left column.
- Chick the Ethernet device in the left column to highlight it for Configuration.
- Click/Verify that the “ON|OFF” indicator in the upper righthand corner is “ON”
- Click the “Configure…” button in the lower righthand corner of the screen.
- The “Editing <devicename>” dialog will appear.
- Click on the “General” Tab.
- Select “Automatically connect to this network when it is available”
- Click the “Save…” button to return to the “Network & HostName” screen.
- (Optionally) Set the Hostname with a Fully-Qualified Domain Name.
- Click “Done” to return to the “Installation Summary” Hub screen.
To fix Issue #2:
- Here is the RHEL documentation concerning the consistent device naming feature
- If you want to suppress the consistent network device naming feature, a kernel boot parameter can now be used: net.ifnames=0
- Otherwise, just get used to the naming, which isn’t actually terrible, in that it uniquely identifies devices by slot number, etc (at least in the PCI,PCIe case) or by built-in numbering (Dell PowerEdge servers, etc).
- Note, this causes the network scripts to have names like:
To fix Issue #3:
- Here is a link to the RHEL knowledgebase article on this issue.
- If you want to go back to the ‘deprecated’ ifconfig util, you can install the net-tools package by executing: yum install net-tools
- Alternately, the “ip” tool can be used (per knowledgebase example text below):
# ip addr show
# ip link show
# ip addr add 10.10.0.123 dev eth1
# ip link set eth1 up
# ip link set eth1 down
# ip route show