The Problem Stale ISCSI target connections which are still present on Initiator node can lead to various issues like: 1. hung iscsid service which can lead to global outage. 2. flood of messages error like: messages:Jun 3 13:58:00 server1 iscsid: iscsid: Connection5:0 to [target: iqn-name, portal: ip-here,3260] through [iface: default] is shutdown. messages:Jun 3 13:58:00 […]
Archives for December 2019
CentOS/RHEL 6 Kernel Panic – “Out of memory” kernel parameter panic_on_oom is enabled
The Problem CentOS/RHEL 6 system reboot due too out of memory error: DUMPFILE: vmcore [PARTIAL DUMP] CPUS: 2 DATE: Mon Feb 29 05:28:02 2016 UPTIME: 33 days, 09:45:55 LOAD AVERAGE: 1.88, 1.52, 1.41 TASKS: 218 NODENAME: localhost RELEASE: 2.6.32-431.el6.x86_64 VERSION: #1 SMP Sun Nov 10 22:19:54 EST 2013 MACHINE: x86_64 (3000 Mhz) MEMORY: 8 GB […]
How to enable core dump for Applications on CentOS/RHEL
1. In CentOS/RHEL core file creation is disabled by default. To enable it, executing the below command: # ulimit -S -c unlimited > /dev/null 2>&1 then execute the program in the same shell environment. 2. To enable it permanently, please follow steps below: – Edit /etc/security/limits.conf. # vi /etc/security/limits.conf * soft core unlimited The ‘*‘ […]
How to add additional language support in CentOS/RHEL
Question: How to add additional language support in CentOS/RHEL? To add specific language support in CentOS/RHEL, you need firstly confirm the correct language group name by “yum grouplist” command. # yum grouplist The available language groups will be displayed in yum output as below: # yum grouplist Loaded plugins: refresh-packagekit, rhnplugin Setting up Group Process […]
What are “segfault” messages in /var/log/messages file
This post explains how to analyse the segfault message in message file and to identify the problem in application or operating system side. What is “segfault”? A segmentation fault (often shortened to segfault) or access violation is a fault raised by hardware with memory protection, to notify operating system (OS) about a memory access violation. […]
Unable to login with GUI on CentOS/RHEL 7
The Problem can’t login to the system via GUI On CentOS/RHEL 7. Also, gdm segfault with below error after which unable to login to GUI. kernel: gdm-simple-slav[4172]: segfault at 0 ip 00007f93d911c7df sp 00007fffecadaac0 error 4 in gdm-simple-slave[7f93d910a000+4a000] kernel: gdm-simple-slav[2645]: segfault at 0 ip 00007f9781f7d7df sp 00007fff672c6980 error 4 in gdm-simple-slave[7f9781f6b000+4a000] The Solution For new […]
rpm: error while loading shared libraries: invalid ELF header
The Problem rpm commands issue the following error: rpm: error while loading shared libraries: /usr/lib64/liblzma.so.0: invalid ELF header The Solution In this instance, either liblzma.so or the link to it (/usr/lib64/liblzma.so.0) had gotten overwritten. $ rpm -qa | grep binutils rpm: error while loading shared libraries: /usr/lib64/liblzma.so.0: invalid ELF header To resolve this issue, the […]
lvremove failing to remove volume after using ‘shred’ command
The Problem When trying to delete volume group by using lvremove, vgremove, pvremove command after executing shred command for physical volume as shown below, fails repeatedly. # shred -vfz -n 3 /dev/sdd # sum -r /dev/sdd 28911 1073741824 When the lvremove command is executed, you will get an error saying that the volume group can […]
How to Configure Network Namespaces in Docker Containers
This post tells how Docker uses network namespace to isolate resources. The following figure is the lab setup to help you understand the steps visually: 1. Create two network namespaces: ns1 and ns2. – Add two new naetwork namespaces: # ip netns add ns1 # ip netns add ns2 The above commands create network space […]
How to change the default IP address of docker bridge
Question: what is the proper procedure to reconfigure the docker interface to use an address range (e.g., > 172.200) for the virtual interfaces it uses? You can reconfigure the default bridge network by providing the bip option along with the desired subnet in the daemon.json (default location at //cdn.thegeekdiary.com/etc/docker/daemon.json ) file as follows: # vi […]