Linux

The Problem All the dnf commands fail with the following error: # dnf repolist Oracle Linux 8 BaseOS Latest (x86_64) 0.0 B/s | 0 B 00:00 Failed to download metadata for repo 'ol8_baseos_latest' Error: Failed to download metadata for repo 'ol8_baseos_latest dnf was not able to refresh the cache as it could not reach the yum server itself, Hence pointing to cache being expired. # yum clean metadata Cache was expired … [Read more...] about Failed to Download Metadata for Repo ‘repo_name’

The following provides the procedure for configuring and using resource groups under Linux: 1. To use cgroups, you must install the "libcgroup" package on your system. # yum install libcgroup 2. Create a config file for cgroups (/etc/cgconfig.conf) and add below configuration. # vi /etc/cgconfig.conf mount { cpu = /cgroup/cpumem; cpuset = /cgroup/cpumem; memory = /cgroup/cpumem; } # High priority group group mysqldb { cpu { # Allocate the relative share of CPU resources … [Read more...] about How to configure Linux Resource Groups (cgroups) for MySQL

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 server1 iscsiadm: iscsiadm: Could not login to [iface: default, target: iqn-name, portal: ip-here,3260]. messages:Jun … [Read more...] about CentOS/RHEL – How to Remove stale ISCSI Target Node Information from ISCSI Initiator Server

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 PANIC: "Kernel panic - not syncing: Out of memory: system-wide panic_on_oom is enabled" PID: 31010 COMMAND: "java" … [Read more...] about CentOS/RHEL 6 Kernel Panic – “Out of memory” kernel parameter panic_on_oom is enabled

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 '*' is used to enable coredump size to unlimited to all users. - Edit /etc/sysctl.conf to add the path of the core dump and file … [Read more...] about How to enable core dump for Applications on 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 Installed Groups: ... Installed Language Groups: Arabic Support [ar] Armenian Support [hy] ... Available … [Read more...] about How to add additional language support in CentOS/RHEL

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. The Linux kernel will response it by performing some corrective action, generally passing the fault to the offending process by sending the … [Read more...] about What are “segfault” messages in /var/log/messages file

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 installation of CentOS/RHEL 7 ,GUI doesnot come with default … [Read more...] about Unable to login with GUI on CentOS/RHEL 7

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 liblzma.so file and associated soft link need to be restored. Follow the steps outlined below … [Read more...] about rpm: error while loading shared libraries: invalid ELF header

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 not be found. # lvremove /dev/VolGroupOracleArch/lvol0 Volume group "VolGroupOracleArch" not found Cannot process volume group VolGroupOracleArch The … [Read more...] about lvremove failing to remove volume after using ‘shred’ command