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
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 Installed Groups: ... Installed Language Groups: Arabic Support [ar] Armenian Support [hy] ... Available … [Read more...] about How to add additional language support in CentOS/RHEL
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. 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
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 installation of CentOS/RHEL 7 ,GUI doesnot come with default … [Read more...] about Unable to login with GUI on CentOS/RHEL 7
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 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
MySQL – How to undo (rollback) a set of SQL statements
What is Conducting a Transaction? If you have a series of SQL statements that you want to run which involve adding, deleting, or changing data contained in InnoDB or BDB tables, but want to be sure that all SQL statements or transactions are completed successfully before committing them, there is a set of MySQL statements that you can use to do this. This is known as conducting a transaction (i.e., the set of SQL statements to execute) and being able to perform a rollback. Currently, you can … [Read more...] about MySQL – How to undo (rollback) a set of SQL statements
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 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
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 by passing a flag to the clone() system call, CLONE_NEWNT. - Check the new created ns: # ip netns list ns2 ns1 When the IP tool creates a network namespace, it … [Read more...] about How to Configure Network Namespaces in Docker Containers
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 /etc/docker/daemon.json ) file as follows: # vi /etc/docker/daemon.json { "bip": "172.200.0.1/16" } Then restart the docker daemon as root. On CentOS/RHEL 6 use the service command to … [Read more...] about How to change the default IP address of docker bridge
“su: Authentication failure” – in Docker
The Problem In some situations, a normal user within a Docker container cannot run 'su' command to switch user. When 'su' command is issued, the following error returns. $ su - Password: [entering correct password] su: Authentication failure The Solution The sticky permission may be missing in /usr/bin/su within the container. With root privilege, you may fix as follows: 1. First check the current permissions for the /usr/bin/su binary file. # ls -l /usr/bin/su -rwxr-xr-x 1 root … [Read more...] about “su: Authentication failure” – in Docker