Post describes procedure to disable IPv6 on CentOS/RHEL 6. There are 2 ways to do this : 1. Disable IPv6 in kernel module (requires reboot) 2. Disable IPv6 using sysctl settings (no reboot required) Method 1 : using /etc/modprobe.d/ipv6.conf 1. Check if IPV6 is enabled: # ifconfig |grep inet6 inet6 addr: fe80::d6be:d9ff:fe99:5a77/64 Scope:Link inet6 addr: fe80::d6be:d9ff:fe99:5a77/64 Scope:Link 2. Create /etc/modprobe.d/ipv6.conf if not already present with below … [Read more...] about CentOS / RHEL 6 : How to disable IPv6
Archives for May 2016
Netbackup Script to get client Vs policy list
Here is a small script to get the list of policies configured against a list of clients using netbackup commandline. Command used is bpplclients to get the clients. Put the list of policy in a file /tmp/policy_list. # cat /tmp/policy_list policy01 policy02 policy03 The script : for i in `cat /tmp/policy_list` do bpplclients $i -noheader | awk 'BEGIN {printf "'$i'"}{print "," $NF}' done > /tmp/output.csv Below is the Output file [ comma (,) separated … [Read more...] about Netbackup Script to get client Vs policy list
Solaris netstat : Understanding the output when displaying routing table
The post describes the meaning of the flags that are displayed in the routing tables when you use the netstat command. Sample output: # netstat -rn Routing Table: Destination Gateway Flags Ref Use Interface -------------------- -------------------- ----- ----- ----- --------- 127.0.0.1 127.0.0.1 UH 021220517 lo0 192.9.200.0 207.82.202.188 UG 0 93 192.9.200.0 207.82.202.65 UG 0 … [Read more...] about Solaris netstat : Understanding the output when displaying routing table
How to Disable or set SELinux to Permissive mode
Question : How to fully disable SELinux (Security Enhanced Linux) or set it to "permissive" mode Answer : SELinux gives that extra layer of security to the resources in the system. It provides the MAC (mandatory access control) as contrary to the DAC (Discretionary access control). Before we dive into setting the SELinux modes, let us see what are the different SELinux modes of operation and how do they work. SELinux can operate in any of the 3 modes : 1. Enforced : Actions contrary to … [Read more...] about How to Disable or set SELinux to Permissive mode
CentOS / RHEL 7 : Booting process
It is important to understanding the Linux boot process to troubleshoot boot problems. These are the high-level steps in the boot process. You need to be aware of files involved in the boot process because errors in these files can cause boot problems. If there is an issue during boot, you need to identify in which phase of boot process the issue lies so that you can take appropriate action to fix the issue. Introduction of systemd systemd is the new system and service manager in … [Read more...] about CentOS / RHEL 7 : Booting process
CentOS / RHEL 7 : How to Change the machine-id
What is machine-id - The /etc/machine-id file contains the unique machine ID of the local system that is set during installation. The machine ID is a single newline-terminated, hexadecimal, 32-character, lowercase machine ID string. When decoded from hexadecimal, this corresponds to a 16-byte/128-bit string. - The "machine-id" parameter is added from RHEL 7.1 to identify the machine in the network. Therefore this parameter must be unique. - But when user clone the virtual machine that is … [Read more...] about CentOS / RHEL 7 : How to Change the machine-id
Solaris 11 : How to configure VLAN tagging on a network interface
A virtual local area network (VLAN) are basically used to isolate groups of users from each other for ease of network administration and security. In Solaris 11, VLANs are created using dladm and the IP address is assigned using ipadm. The post describes configuration of VLAN tagging on network interface with an example. Configuration To list out the physical network interfaces on the system use: # dladm show-phys LINK MEDIA STATE SPEED DUPLEX … [Read more...] about Solaris 11 : How to configure VLAN tagging on a network interface
How to Check whether SELinux is Enabled or Disabled
Question : How to Check whether SELinux is Enabled or Disabled Answer : SELinux gives that extra layer of security to the resources in the system. It provides the MAC (mandatory access control) as contrary to the DAC (Discretionary access control). Before we dive into setting the SELinux modes, let us see what are the different SELinux modes of operation and how do they work. SELinux can operate in any of the 3 modes : 1. Enforced : Actions contrary to the policy are blocked and a … [Read more...] about How to Check whether SELinux is Enabled or Disabled
Downloading a Specific Version of Package and Its Dependencies from Repository for Offline Installation Using YUM
Question : How to download a specific version of the package along with its dependencies using YUM offline. Answer : 1. To see what particular versions are available to you via yum you can use the --showduplicates switch. # yum --showduplicates list [package_name] For Example : # yum --showduplicates list httpd Loaded plugins: product-id, security, subscription-manager. Installed Packages httpd.x86_64 2.2.15-39.0.1.el6 @ol6_x86_64_latest --- installed Available … [Read more...] about Downloading a Specific Version of Package and Its Dependencies from Repository for Offline Installation Using YUM
CentOS / RHEL : Exclusion with Yum For Kernel Updates
Question : How to make an exclusion list so that anyone running the command "yum update" will not download any kernel patches ? Answer : This can be done using 2 ways : 1. yum configuration file yum.conf (permanent) 2. Using command line options Using yum.conf 1. From the man page of yum.conf : # man yum.conf exclude List of packages to exclude from updates or installs. This should be a space separated list. Shell globs using wildcards (eg.* and ?) are allowed. 2. This would need … [Read more...] about CentOS / RHEL : Exclusion with Yum For Kernel Updates