How to Ensure Red Hat GPG Key is Installed.
To ensure that the system can cryptographically verify update packages (and also connect to the Red Hat Network to receive them if desired), run the following command to ensure that the system has the Red Hat GPG key properly installed:
Example below shows on a Centos Server.
[centos@mail ~]$ rpm -q –queryformat “%{SUMMARY}\n” gpg-pubkey
gpg(CentOS-6 Key (CentOS 6 Official Signing Key) )
gpg(Dag Wieers (Dag Apt Repository v1.0) )
[centos@mail ~]$
The command should return the string: gpg(Red Hat, Inc. (release key ) for redhat systems.
Disable IPv6 in RHEL5
Unless your policy or network configuration requires it, disable IPv6.
To do so, prevent the kernel module from loading by adding the following line to
/etc/modprobe.conf
Next, add or change the following lines in /etc/sysconfig/network:
NETWORKING_IPV6=no
IPV6INIT=no
How can I get yum to keep package at a certain version.
There are several ways you can do this.
One is to exclude it from your updates list. See man yum.conf for more details.
Another way to pin package to a certain version is to use the versionlock plugin.
If you are using the latest Fedora then the plugin can be installed using:
yum install yum-plugin-versionlock
To add files that you want version locked, use the following yum command:
yum versionlock [package-name]
virtualization with Red Hat Enterprise Linux - System requirements.
This chapter lists system requirements for successfully running virtualization with Red Hat Enterprise Linux. Virtualization is available for Red Hat Enterprise Linux 5 Server.
The requirements for virtualization vary depending on the type of hypervisor. The Kernel-based Virtual Machine (KVM) and Xen hypervisors are provided with Red Hat Enterprise Linux 5. Both the KVM and Xen hypervisors support Full virtualization. The Xen hypervisor also supports Para-virtualization.
Minimum system requirements
6GB free disk space
2GB of RAM.
Recommended system requirements
6GB plus the required disk space recommended by the guest operating system per guest. For most operating systems more than 6GB of disk space is recommended.
One processor core or hyper-thread for each virtualized CPU and one for the hypervisor.
2GB of RAM plus additional RAM for virtualized guests.
Understanding DNSBL Filtering
A DNSBL (commonly known as a ‘Blocklist”) is a database that is queried in realtime by Internet mail servers for the purpose of obtaining an opinion on the origin of incoming email. The role of a DNSBL such as Spamhaus’ SBL/XBL/PBL Advisory system is to provide an opinion, to anyone who asks, on whether a particular IP Address meets Spamhaus’ own policy for acceptance of inbound email.
The policy of the Receiver governs whether a message is blocked or not
Every Internet network that chooses to implement spam filtering is, by doing so, making a policy decision governing acceptance and handling of inbound email. The Receiver unilaterally makes the choices on whether to use DNSBLs, which DNSBLs to use, and what to do with an incoming email if the email message’s originating IP Address is “listed” on the DNSBL. The DNSBL itself, like all spam filters, can only answer whether a condition has been met or not.
