Author: admin

How to copy an instance between two Openstack environments

Turn off the instance, and then using the nova image-create command, create a snapshot of the nova instance. openstack server list openstack server image create server2 --name server2-snapshot After the snapshot is created, it will be visible at a glance. Confirm snapshot in a glance with; openstack image list Download snapshot image openstack image save …

Read more

How to clear ceilometer in OpenStack

To clean up old ceilometer data in OpenStack, perform the following steps: First of all, stop the Telemetry service. systemctl stop openstack-ceilometer-collector openstack-ceilometer-notification openstack-gnocchi-metricd openstack-gnocchi-statsd openstack-aodh-evaluator openstack-aodh-listener openstack-aodh-notifier openstack-ceilometer-central Stop MongoDB service by entering the following on shell prompt. systemctl stop mongod Delete all files in /var/lib/mongodb and then restart MongoDB. cd /var/lib/mongodb rm -r …

Read more

How to install NVIDIA driver (proprietary) and uninstall Nouveau driver (open source) in Linux server

Start your Linux server in text mode. GUI mode will give an error while uninstalling the Nouveau driver or installing the NVIDIA driver. Remove Nouveau driver: Open /etc/default/grub in text editor [vi] and add the following option to GRUB_CMDLINE_LINUX modprobe.blacklist=nouveau On root shell, execute the following command to build the /boot/grub2/grub.cfg as follows: grub2-mkconfig -o …

Read more

Change hostname and IP address of Linux server without rebooting server

You can change option in third line in /etc/hosts file on Linux server without rebooting; /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.0.1 server.seimaxim.com seimaxim You can change all of the following options in /etc/sysconfig/network without reboot. /etc/sysconfig/network NETWORKING=yes HOSTNAME=server.seimaxim.com GATEWAY=192.168.0.1 Similarly options in /etc/sysconfig/network-scripts/ifcfg-eth0 can also be changed. /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 …

Read more

Error while configuring IP in ifcfg-eth0 on Linux Server “RTNETLINK answers: network is unreachable”

This error may arise if the IP address and Gateway subnets are different. Make sure both IP address and Gateway have the same subnets. For reference, the ifcfg-eth0 configuration file is given below. TYPE="Ethernet" PROXY_METHOD="none" BROWSER_ONLY="no" BOOTPROTO="none" DEFROUTE="yes" IPV4_FAILURE_FATAL="no" IPV6INIT="yes" IPV6_AUTOCONF="yes" IPV6_DEFROUTE="yes" IPV6_FAILURE_FATAL="no" IPV6_ADDR_GEN_MODE="stable-privacy" NAME="eth0" UUID="3d9bd3c7-310c-4e46-a57c-5b3a99819f78" DEVICE="eth0" ONBOOT="yes" IPADDR="37.48.96.245" PREFIX="27" GATEWAY="37.48.96.254" DNS1="8.8.8.8" IPV6_PRIVACY="no" Remove route …

Read more

Rebuild initial ramdisk image in Linux server – How-To

You may need to rebuild initial ramdisk image after adding new hardware or software to server. Create backup as shown below; cp /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).bak.$(date +%m-%d-%H%M%S).img Use following command to rebuild initramfs dracut -f -v Make sure /boot/grub2/grub.cfg and /etc/grub2.cfg includes the menu to the new custom initramfs Rebuild grub.cfg; grub2-mkconfig -o /boot/efi/EFI/seimaxim/grub.cfg

Read more

Adding disk space from non-root-LVM to root-LVM

All users should be logged out of server except root. Fsck the filesystem. Reduce the non-root LVM by entering following command on root shell; lvresize --resizefs --size lvresize --resizefs --size -200G /dev/VolGroup00/LogVoL-USER After non-root LVM filesystem is reduced, increase the root-LVM filesystem using; lvresize --resizefs --size +500M /dev/VolGroup00/LogVol-ROOT Mount the filesystem.

Read more

Disable Transparent Huge Pages [THP] in CentOS 8

On CentOS 8, In file editor open /etc/default/grub file, and add “transparent_hugepage=never” kernel parameter on the GRUB_CMDLINE_LINUX in options as shown below; GRUB_CMDLINE_LINUX="options transparent_hugepage=never" On command line execute grub2-mkconfig to build /boot/grub2/grub.cfg grub2-mkconfig -o /boot/grub2/grub.cfg [System with BIOS] grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg [System with UEFI] Reboot Server to apply changes. If THP is still not disabled, …

Read more

How to configure a SSH tunnel?

On the client machine perform the following step: [root@host]# ssh -N -L :: user@remote-machine-ip From a new console/terminal execute the telnet command as follows: [root@host]# telnet localhost This kb is relevant to the following; Encrypt the traffic by SSH tunneling the connection to remote host. Encrypt unencrypted network traffic

Read more