This is the procedure on how to replace broken disk from zfs raid array. In this case we simulate to replace zfs raid-1.

  • Check zfs pool status
    #zfs status -v
  • Get the disk information and replaced it (Let’s say that the failed disk is /dev/sdb)
  • Clone the disk partition table from the health disk to replacement
    #sgdisk -R /dev/sdb /dev/sda [newdisk - existing disk]
  • Regenerate the partition UID
    #sgdisk -G /dev/sdb
  • Replacing the disk
    #zpool replace rpool /dev/sdb2 /dev/sdb2
  • Monitoring resilvering process, the
    #zpool status -v
  • For the disk where boot partition resided, make sure to update the grub configuration to mark the replaced disk
    #dpkg-reconfigure grup-pc
    #Make sure to check the new disk.

Thank You

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P.

Passing LFCS Exam (Re-write)

This December 2019, i have passed the Linux Foundation Certified System (LFCS) Administrator exam. This exam is provided by Linux Foundation Organization. An organization to maintain the open source ecosistem by provide an event, training and certification.

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For more details, you can visit their site here. For the Lxcf exam, here.
Having prior experience in using Linux/Unix based OS is must. Especially understand how this Operating System works generally and how to use the command line. Most of the question/task in this exam is hands-on Linux command.

For the LFCS Exam, a score of 66% or above must be earned to pass. FAQ for Linux Foundation here.

The number of the question on this exam is slightly different from each person. Seems based on the question/task weight and scoring. In my case, i have about 65-70 question.

The question domain based on my exam is;
– User/group management
– Storage management
– File manipulation
– Other’s command
By the way we can chose 2 distribution for this exam, Cent-OS/Ubuntu.

For this exam, i used the bundle package exam + course with Black Friday coupon 😀 though. But, the course is only general course how the Linux working.



L.

Linux backup using Rsync (Updated)

This time is about using rsync to copy a Linux/Unix system to another host or backing it up. By using rsync, its more effective than using tool like dd since we can efficiently select the directory, attribute that we we want to backup or move.

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The one who not so wise

rsync also can be use when the system is running. But you may need to do it with caution and make sure you understand the data state. When rsync with the system running, the data that have not commit the changes in files level may not transfer.

This method is work for migrating the the system to another hosts. Please be aware, that the target is the fresh installed operating system with the same version of the source.

Rsync full backup

# rsync -aAXHv --numeric-ids --info=progress2 --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found"} / /path/to/backup

Rsync Clone

rsync -qaHAXS [SOURCE_DIR] [DESTINATION_DIR]
  • –numeric-ids, will disable mapping of user and group names; instead, numeric group and user IDs will be transfered. This is useful when backing up over SSH or when using a live system to backup different system disk.
  • –info=progress2,  will show the overall progress info and transfer speed instead of the list of files being transferred.
  • avoid crossing a filesystem boundary when recursing, add the option -x/--one-file-system. This will prevent backing up any mount point in the hierarchy.
  • -n or known as the option for the dry-run. To simulate the file transfers

Tips:

When migrating operating system using rsync, we may need to make sure that the migration have a low downtime impact on the server/service. Make sure you perform inital rsyn using above command in “Rsync full backup”. Then at the final migration, stop all service on the source server/vm then perfom the same command again.

To avoid saturated network performance when transfering the you can use option to have a speed limit in the transfer  –bwlimit= [In KBytes]