Reinstalling GRUB 2 from LiveCD

By -
If you cannot boot from GRUB 2 and need to reinstall it, here is the simple method. For more details or for advanced options, refer to the Ubuntu community documentation here: Grub2 - Reinstalling GRUB 2:
  • Boot the Ubuntu Live CD (Try without installing).
  • From the Desktop, open a terminal - Applications, Accessories, Terminal.
  • Determine your normal system partition - `sudo fdisk -l` (That is a lowercase L)
  • If you aren't sure, run `df -Th`. Look for the correct disk size and ext3 or ext4 format.
  • Mount your normal system partition:
    Code:
    sudo mount /dev/sdXY /mnt
    • If you aren't sure if you mounted the correct partition, once it's mounted run "nautilus /mnt" to inspect the partition. If it is the correct partition, you should see the normal Ubuntu folders such as /bin, /boot, /etc, /home, etc
    • Example: sudo mount /dev/sda1 /mnt
    • Note: The partition to mount is normally the partition on which Ubuntu was installed: sda1, sdb5, etc. If you have a separate /boot partition, use the device on which the /boot partition is located. Grub 2 works best when installed in the MBR of the drive to which BIOS boots. Also remember that you mount the partition (including the number) in this step, but you do not include the partition number when you run the "sudo grub-install" command later.
    • Note: GRUB 2 counts the first drive (X) as "0", but the first partition (Y) as "1"
  • Only if you have a separate boot partition:
    • Code:
      sudo mount /dev/sdXY /mnt/boot
      with sdXY being your /boot partition designation.
  • Reinstall GRUB 2:
    Code:
    sudo grub-install --root-directory=/mnt /dev/sdX
    Do NOT include the partition number.
    • Example: sudo grub-install --root-directory=/mnt /dev/sda
    • Note: Substitute the device on which Ubuntu was installed - sda, sdb, etc. Do not specify a partition number.
  • Unmount the partition *:
    Code:
    sudo umount /mnt
    • * Note: If you mounted a separate /boot partition, unmount it first:
      Code:
      sudo umount /mnt/boot
  • Reboot.

Comments

Post a Comment

Popular posts from this blog

CEPH bluestore using ceph-ansible

By -
Just to test the ceph bluestore i have created 2 virtual machine in virtualbox with hostname: admin & osd1. Attached the 2 10G hdd for the OSD's in both the nodes. Below are the commands that i used to deploy it using the ceph-ansible: git clone https://github.com/ceph/ceph-ansible cd ceph-ansible cp group_vars/osds.yml.sample group_vars/osds.yml cp group_vars/all.yml.sample group_vars/all.yml cp group_vars/mons.yml.sample group_vars/mons.yml cp site.yml.sample site.yml vi group_vars/osds.yml     devices:    - /dev/sdb     - /dev/sdc bluestore : true vi group_vars/all.yml ceph_stable: true ceph_mirror: http://download.ceph.com/ ceph_stable_key: https://download.ceph.com/keys/release.asc ceph_stable_release: kraken ceph_stable_repo: "{{ ceph_mirror }}/rpm-{{ ceph_stable_release }}" monitor_interface: enp0s3 monitor_address: 192.xx.xx.xx osd_objectstore: bluestore ceph_conf_overrides:  ...
Read more

Start wildfly service with standalone-full.xml

By kris -
Wildfly provides a service.bat in %WILDFLY_HOME%\bin\service. Calling the batch file with the install parameter installs Wildfly as a service on Windows. Once it is installed on windows, you can change the settings so that wildfly starts all the modules and services instead of default minimal setup. For this, change standalone.bat file and add this line : set "SERVER_OPTS=--server-config=standalone-full.xml" This will enable startup of all modules & services of wildfly from now on.
Read more

Scan FC LUN's in RHEL/CentOS

By -
1.First find out how many disks are visible in “fdisk -l” . # fdisk -l 2>/dev/null | egrep '^Disk' | egrep -v 'dm-' | wc -l 2.Find out how many host bus adapter configured in the Linux box.you can use “systool -fc_host -v” to verify available FC in the system. # ls /sys/class/fc_host host0 host1 In this case,you need to scan host0 & host1 HBA. 3.If the system virtual memory is too low ,then do not proceed further.If you have enough free virtual memory,then you can proceed with below command to scan new LUNS. # echo "1" > /sys/class/fc_host/host0/issue_lip # echo "1" > /sys/class/fc_host/host1/issue_lip Note:   You need to monitor the “issue_lip” in /var/log/messages to determine when the scan will complete.This operation is an asynchronous operation. 4.Verify if the new LUN is visible or not by counting the available disks. # fdisk -l 2>/dev/null | egrep '^Disk' | egrep -v 'dm-' | wc -l If any new...
Read more