ASM files can be renamed like any other files in a standard filesystem. For ASM, rename is performed through some type of statements (ADD ALIAS, RENAME ALIAS, ADD DIRECTORY) to manipulate filenames, alias, and directories. Renaming datafiles is sometimes needed when database file names still contain old database name after a database on ASM is […]
Archives for April 2018
How To Check a Disk for Bad Blocks or Disk Errors on CentOS / RHEL
Hard disks can fail unexpectedly and it is always best to keep recent backups of all important data. Please keep in mind that even if a current or oncoming failure is detected, there may not be enough time to backup the data. Below are several methods that can be used to identify bad blocks or […]
Run Docker as a non-root user
The Docker containers by default run with the root privilege and so does the application that runs inside the container. This is another major concern from the security perspective because hackers can gain root access to the Docker host by hacking the application running inside the container. Method 1 – Add user to Docker group […]
How to Configure Btrfs as the Storage Engine in Docker
Docker is an open platform management tool for Linux Containers. It provides a means for developers and system administrators to build and package applications into lightweight containers. Docker uses devicemapper devices as the default storage engine. To use Btrfs as the storage engine, perform the following steps. Note that Red Hat Enterprise Linux (RHEL) removes […]
How to check failed or bad login attempts in Linux
Invalid login attempts can be tracked using command lastb provided the file /var/log/wtmp is present. Some of the possible causes for incorrect or bad login attempts are given below: due to typo wrong password has been entered during login. password has changed of user used in cron to connect via ssh. If any hacker is […]
How to create Docker Image from a Container and Dockerfile
Docker is an open platform management tool for Linux Containers. It provides a means for developers and system administrators to build and package applications into lightweight containers. Docker consists of the following components: Docker Engine – A portable, lightweight runtime and packaging tool Docker Hub – A cloud service for sharing applications and automating workflows […]
Beginners Guide to The Docker World
Docker: Introduction Docker is an open platform management tool for Linux Containers. It provides a means for developers and system administrators to build and package applications into lightweight containers. Docker consists of the following components: Docker Engine – A portable, lightweight runtime and packaging tool Docker Hub – A cloud service for sharing applications and […]
Beginners Guide to Udev in Linux
Udev is the device manager for the Linux kernel. Udev dynamically creates or removes device node files at boot time in the /dev directory for all types of devices. Udev is now part of systemd as you can see by viewing the “udev” file names included with the systemd RPM package. # rpm -ql systemd […]
How to Check and Analyze Memory Usage in Solaris
Troubleshooting performance issues is an important skill every system admin must have. This post is intended to give hints, where to look for in checking and troubleshooting memory usage. In principle, investigation of memory usage is split in checking usage of kernel memory and user memory. Please be aware that in case of a memory-usage […]
Manual Changes Made To /etc/hosts Or /etc/sysconfig/network-scripts/ifcfg-* Are Lost
The Problem You directly edit the /etc/hosts file, the /etc/resolv.conf file, or the /etc/sysconfig/network-scripts/ifcfg-* files. After a few minutes or a reboot, your changes are lost and the files revert to a previous form. The Solution The Red Hat Enterprise Linux (RHEL) distributions include the NetworkManager RPM package. This provides a daemon which monitors the […]