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Managing-quotas-LVM-and-RAID.md

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Quota Management in Linux

Quota management in Linux is used to restrict and monitor disk space and inode usage by users and groups on a filesystem. It helps prevent a single user or process from consuming excessive resources.

Enabling Disk Quotas

Install Quota Package

  • Debian-based systems:

    sudo apt install quota -y

  • RHEL/CentOS:

    sudo yum install quota -y

  • Fedora:

    sudo dnf install quota -y

Enable Quotas on a Filesystem

Modify /etc/fstab File

Add quota options for the desired partition:

/dev/sdb1 /d1 ext4 defaults,usrquota,grpquota 0 0

Remount the Filesystem

sudo mount -o remount /d1

Create Quota Database

Run the following command to check and create the quota database:

sudo quotacheck -cum /home

Command Breakdown:

  • c: Create quota files
  • u: Check user quotas
  • m: Do not remount the filesystem as read-only

Enable Quota

  1. Initialize quotas on the filesystem: 
    sudo quotaon /d1
  2. Verify quota status: 
    sudo quota -ap

Additional Commands and Tools

  1. Check Block Device Information:

    lsblk
blkid
df -h

  2. Format Filesystem:

    sudo mkfs.ext4 /dev/sdb1
sudo mkfs.xfs /dev/sdb1

  3. Quota Management Commands:

    • quotacheck -cum /d1: Check and create quota files
    • quotacheck -cugv /d2: Check quotas for users and groups
    • quota -ap: Display all quotas
    • edquota username: Edit user quotas
    • touch /d1/aquota.user /d1/aquota.group: Create required quota files
    • tune2fs -O quota /dev/sdb1: Enable quota feature on ext4 filesystem

Logical Volume Manager (LVM) and RAID Setup and Management

Logical Volume Manager (LVM) is a storage management solution in Linux that provides flexibility and advanced features for managing disk space. It allows dynamic resizing of partitions.

LVM Setup and Management Guide

Key Components of LVM

  • Physical Volume (PV): The actual storage device (e.g., /dev/sdb, /dev/sdc).
  • Volume Group (VG): A pool of storage created from one or more PVs.
  • Logical Volume (LV): A partition-like structure inside a VG, where file systems are created.

Setting Up LVM

Step 1: Install LVM (If Not Installed)

  • Debian/Ubuntu: 
    apt install lvm2 -y
  • RHEL/CentOS: 
    yum install lvm2 -y

Verify Installation:

  • Check installed packages: 
    rpm -qa | grep lvm2
  • List package files: 
    rpm -ql | grep lvm2
  • Display package information: 
    rpm -qi lvm2

Disk Preparation

  • Free the disk: 
    fdisk /dev/sdb
  • Create a single partition: 
    fdisk /dev/sdb
  • Check system block devices: 
    lsblk
  • View mounted filesystems: 
    df -h
  • Edit fstab (remove any unwanted entries): 
    vim /etc/fstab

Step 2: Create Physical Volume

  • Identify available disks: 
    lsblk
  • Initialize the disk as an LVM physical volume: 
    pvcreate /dev/sdb /dev/sdc
  • Display physical volume details: 
    pvdisplay
  • Verify physical volumes: 
    pvs

Step 3: Create a Volume Group

  • Create a volume group named vg_data: 
    vgcreate vg_data /dev/sdb /dev/sdc
  • Display volume group details: 
    vgdisplay

Step 4: Create a Logical Volume

  • Create a 60 GB logical volume named lv_storage: 
    lvcreate -L 60G -n lv_storage vg_data
  • Check the logical volume content: 
    lvs

Step 5: Formatting and Mounting the LVM Partition

  • Format the logical volume: 
    mkfs.ext4 /dev/vg_data/lv_storage
  • Create a mount point: 
    mkdir /mnt/storage
  • Mount the logical volume: 
    mount /dev/vg_data/lv_storage /mnt/storage
  • Verify the block devices: 
    lsblk
  • Check filesystem UUID: 
    blkid
  • Verify the mount: 
    df -h
  • Copy logs as a test: 
    cp -vr /var/log/* /mnt/storage
  • List contents: 
    ls -lh /mnt/storage

Resizing Logical Volumes

Extend an LV (Increase Size)

  • Extend the logical volume by 10 GB: 
    lvextend -L +10G /dev/vg_data/lv_storage
  • Resize the filesystem: 
    resize2fs /dev/vg_data/lv_storage
  • Verify the change: 
    df -h /mnt/storage

Shrink an LV (Reduce Size)

  • Unmount the volume: 
    umount /mnt/storage
  • Check and reduce the filesystem: 
    e2fsck -f /dev/vg_data/lv_storage
resize2fs /dev/vg_data/lv_storage 15G
  • Reduce the logical volume size: 
    lvreduce -L 15G /dev/vg_data/lv_storage
  • Remount the volume: 
    mount /dev/vg_data/lv_storage /mnt/storage

Mounting Snapshots

  • Mount the snapshot: 
    mount /dev/vg_data/lv_snapshot /mnt/snapshot
  • Remove the snapshot after use: 
    umount /dev/vg_data/lv_snapshot
lvremove /dev/vg_data/lv_snapshot

Removing LVM Components

Remove a Logical Volume

  • Unmount the logical volume: 
    umount /mnt/storage
  • Remove the logical volume: 
    lvremove /dev/vg_data/lv_storage
  • Verify removal: 
    lvdisplay