Chris Paquin

AI, Virtualization, Containers, Infrastructure, Linux

Category: rhel7

  • RHEL7: Registering a System with the Red Hat Network Using Subscription Manager

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    Note that I am about to give you the simpletons version of registering a system. Expect nothing fancy below. In  this post I will do my best to keep it brief.

    If you need to register newly build RHEL 7 system using Subscription Manger rather than the ‘rhn_register’ command (which is pretty much deprecated) you will need to run the command as shown below. Including the option  “–auto-attach“ is pretty much the simplest method to register with RHN, as you  do not need to keep track of any of your subscription names.

    [root@rhel7 ~]#  subscription-manager register –username <username> –password <password> –auto-attach

    Once auto-attached you can log into rhn.redhat.com, and use the WebUI to pick and choose any additional subscriptions that you want to attach.

    Once you have attached as many subscriptions as your heart desires (or you are licensed for) ,you can then run the following command to see each and every yum repository that you have access to, even if they are disabled.

    [root@rhel7 ~]# yum repolist all

    Depending on the number of repos that you have access to, so you might want to narrow the list down a bit, as shown below.

    [root@rhel7 ~]# yum repolist all | grep -i openstack-6

    rhel-7-server-openstack-6.0-debug-rpms/7Server/x86_64                           disabled
    rhel-7-server-openstack-6.0-installer-debug-rpms/7Server/x86_64             disabled
    rhel-7-server-openstack-6.0-installer-rpms/7Server/x86_64                        disabled
    rhel-7-server-openstack-6.0-installer-source-rpms/7Server/x86_64            disabled
    rhel-7-server-openstack-6.0-rpms/7Server/x86_64                                      disabled
    rhel-7-server-openstack-6.0-source-rpms/7Server/x86_64                          disabled

    Now you can enable the repos that you need with the command below. Note that the enable option accepts wildcards, but also note the discrepancy in the repo names in the command output above, and in the command below. If you are not passing a wildcard option on the enable command, then you will need to modify the repo names before you can run your command with any bit of success.

    [root@rhel7 ~]# subscription-manager repos –enable rhel-7-server-openstack-6.0*
    Repository ‘rhel-7-server-openstack-6.0-rpms’ is enabled for this system.
    Repository ‘rhel-7-server-openstack-6.0-source-rpms’ is enabled for this system.
    Repository ‘rhel-7-server-openstack-6.0-debug-rpms’ is enabled for this system.
    Repository ‘rhel-7-server-openstack-6.0-installer-debug-rpms’ is enabled for this system.
    Repository ‘rhel-7-server-openstack-6.0-installer-source-rpms’ is enabled for this system.
    Repository ‘rhel-7-server-openstack-6.0-installer-rpms’ is enabled for this system.

  • RHEL7 – How to Set Your Hostname in Redhat Enterprise Linux 7

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    Setting a server’s hostname used to be as simple as running the ‘hostname’ command and adding a “HOSTNAME” entry in /etc/sysconfig/network. However things have changed quite a bit in RHEL7. Apparently, systemd now controls setting a server’s hostname. The ‘hostname‘ command no longer works to set your hostname, however the command is still available just to confuse you.

    Now in RHEL 7 you use the command ‘hostnamectl‘. Below is an example of how it works.

    Here I have logged into my a RHEL 7.1 VM. You can see that the system appears to have the hostname of node1.

    [root@node1 ~]# hostname
    node1

    However upon further inspection, I find that this is not the case. Rather, the server has a static hostname of localhost.localdomain.

    [root@node1 ~]# hostnamectl
    Static hostname: localhost.localdomain
    Transient hostname: node1
    Icon name: computer-vm
    Chassis: vm
    Machine ID: 4c26a2a3101947bfa2ec7d9c16824ca4
    Boot ID: f58707942bd1458da48680025b6f1a53
    Virtualization: vmware
    CPE OS Name: cpe:/o:redhat:enterprise_linux:7.1:GA:server
    Kernel: Linux 3.10.0-229.el7.x86_64
    Architecture: x86_64

    So lets set the hostname permanently using ‘hostnamectl’.

    [root@node1 ~]# hostnamectl set-hostname node1.packy.lab.localdomain

    As you can see the hostname shows correct in the output of the ‘hostname’ command

    [root@node1 ~]# hostname
    node1.packy.lab.localdomain

    … and in the output from ‘hostnamectl’

    [root@node1 ~]# hostnamectl
    Static hostname: node1.packy.lab.localdomain
    Icon name: computer-vm
    Chassis: vm
    Machine ID: 4c26a2a3101947bfa2ec7d9c16824ca4
    Boot ID: f58707942bd1458da48680025b6f1a53
    Virtualization: vmware
    Operating System: Employee SKU
    CPE OS Name: cpe:/o:redhat:enterprise_linux:7.1:GA:server
    Kernel: Linux 3.10.0-229.el7.x86_64
    Architecture: x86_64

  • Fedora21 – Quick and Dirty with Firewalld

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    Hey, are you new to Firewalld like most of us?

    Unless you have been using Firewalld in the last few releases of Fedora, as some out there have, then you probably could probably use a few pointers to get you started on your way to configuring your Linux firewalls the “new-fangled fancy way”. This is especially the case if you plan on moving to RHEL7 anytime soon — as Firewalld is the default there. So put on your big boy (or girl) pants and say goodbye to your old friend IPTABLES.

    According to this page. Firewalld is…

    “The dynamic firewall daemon firewalld provides a dynamically managed firewall with support for network “zones” to assign a level of trust to a network and its associated connections and interfaces. It has support for IPv4 and IPv6 firewall settings. It supports Ethernet bridges and has a separation of runtime and permanent configuration options. It also has an interface for services or applications to add firewall rules directly”

    Wow, how fancy. So how do we use it? Well let’s take a stab at enabling HTTP access to our Fedora21 workstation.

    First thing first, lets figure out what our default done is on our workstation.

    $ sudo firewall-cmd –get-default-zone
    FedoraWorkstation

    Ok, thats a bit strange, in RHEL you should expect PUBLIC to be your default zone.  Now that we know what zone we need to mess with let’s make sure that its applied to the proper interfaces.

    $ sudo firewall-cmd –get-active-zone
    FedoraWorkstation
    interfaces: enp4s0 enp5s4 macvtap0 tun0 virbr0

    The first two interfaces above are our physical interfaces, so we are good here. Now lets apply the rule, and make sure its permanent.

    $ sudo firewall-cmd –permanent –zone=FedoraWorkstation –add-service http
    success

    Now lets check our rules. Note HTTP is missing.

    $ sudo firewall-cmd –list-services
    dhcpv6-client mdns samba-client ssh

    Since we have only applied this new rule to our permanent config and not to our running config, we need to restart firewalld to see the updated rule.

     $ sudo firewall-cmd –reload

    Now your can view the updated rules…

    $ sudo firewall-cmd –list-services
    dhcpv6-client http mdns samba-client ssh