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Linux - Storage: Partition

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• Linux - Storage: Partition
  • Partition
    • Types of Partitions
    • Partitioning Schemes
    • Thin Provisioning
    • Geting Disk Device Info
  • Configuration File
    • /etc/mtab
    • /proc/partitions
  • Common Commands
    • parted: Manage Partitions
    • Lab: Create new parition
    • fdisk: Manage Partitions
    • mkfs: Format a partition
    • mount: Attach a Filesystem
  • Lab: Create and Attach a New Partition
    • Add the New Disk to the VM
    • Identify the New Disk in Linux
    • Partition the New Disk
    • Create a Filesystem
    • Mount the New Partition
    • Persist the Mount in /etc/fstab
  • Lab: Unmount an Existing Partition
  • Lab: Mount all partition mentioned in /etc/fstab

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Partition

• Partition

  • a logical division of a physical storage device (e.g., a hard disk or SSD).
  • allows a single physical disk to be divided into separate sections, each functioning as an independent unit for organizing data.
    • can exist on a portion of a disk, on an entire disk, or it may span multiple disks.

• Benefits:

  • To separate the operating system, user data, and application files.
  • To install multiple operating systems on a single disk.
  • To optimize performance by allocating specific partitions for swap or log files.
  • To enable different filesystem types for different purposes.

• Partitioning information

  • stored at special disk locations that the system references at boot time.

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Types of Partitions

• Primary Partition:
  • A disk can have up to 4 primary partitions.
  • Each primary partition can directly hold data or an operating system.
• Extended Partition:
  • A special type of primary partition that can contain multiple logical partitions.
  • Used to overcome the 4-partition limit.
• Logical Partition:
  • Sub-partitions within an extended partition.
  • Can be used for additional filesystems, swap space, etc.

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Partitioning Schemes

• MBR (Master Boot Record):
  • Older partitioning scheme, supports up to 4 primary partitions.
  • Maximum disk size: 2 TB.
• GPT (GUID Partition Table):
  • Modern scheme, supports unlimited partitions (typically 128 by default).
  • Handles disks larger than 2 TB.

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Thin Provisioning

• Thin provisioning technology
  • allows for an economical allocation and utilization of storage space by moving arbitrary data blocks to contiguous locations, which results in empty block elimination.

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• Partition Files

  • Partitions are represented as special files in Linux:
  • e.g.,
    • /dev/sda1 - First partition on the first disk.
    • /dev/sdb2 - Second partition on the second disk.

• Commands

  • fdisk: For MBR disks.
  • parted: For both MBR and GPT disks.
  • lsblk: To view partition layout.

• Partition Lifecycle

  • Create: Use fdisk or parted to define partitions.
  • Format: Apply a filesystem (mkfs.ext4, mkfs.xfs).
  • Mount: Attach the partition to the system’s directory structure (mount /dev/sda1 /mnt).

• Common Partitions

  • Root Partition (/): Contains the operating system files.
  • Boot Partition (/boot): Contains boot loader files
  • Swap Partition: Acts as virtual memory.
  • Home Partition (/home): Stores user-specific data.

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Geting Disk Device Info

CMD	DESC
lsblk	List all block devices, including disks and partitions.
fdisk -l	List disks and partitions.
parted -l	List disks and partitions.
blkid	Get UUIDs and filesystem types for all devices.
df -h	Display disk space usage of mounted filesystems

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Configuration File

/etc/mtab

• /etc/mtab

  • Mount Table
  • dynamically records all currently mounted filesystems and their details.
  • Provides information about active mounts on the system.
  • Includes mounts not listed in /etc/fstab, such as temporary or user-specific mounts.

• Structure

  • Each line in /etc/mtab represents a mounted filesystem with details similar to /etc/fstab, but dynamically updated.

Field	Description
Device	Mounted device or remote filesystem.
Mount Point	Where the filesystem is mounted.
FS Type	The type of filesystem.
Mount Options	Options used for the mount.

• Example

/dev/sda1 /     ext4  rw,relatime       0   0
/dev/sda2 /home ext4  rw,relatime       0   0
tmpfs     /tmp  tmpfs rw,nosuid,nodev   0   0

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/proc/partitions

• /proc/partitions:

  • contains partition block allocation information.

• Sample

major minor  #blocks  name

 259        0   20971520 nvme0n1
 259        1     614400 nvme0n1p1
 259        2    1048576 nvme0n1p2
 259        3   19306496 nvme0n1p3
 253        0   17207296 dm-0
 253        1    2097152 dm-1
   8        0    1048576 sda
   8        1      97280 sda1

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Common Commands

parted: Manage Partitions

• parted

  • disk partitioning tool used to create, modify, delete, and manage partitions on a disk.
  • supports both MBR and GPT schemes
  • supports to create up to 128 partitions on a single GPT disk.

• Common Partition table type:

  • gpt: provides support for GUID partition tables;
  • msdos: provides support for DOS-style MBR partition tables;

• Common Flags

  • boot :Marks the partition as bootable.
  • esp: Marks an EFI System Partition (for UEFI boot).
  • lvm Indicates the partition is used by LVM (Logical Volume Manager).
  • swap: Marks the partition as swap space.
  • raid: Marks the partition as part of a RAID array.
  • hidden： Hides the partition from the OS.
  • msftres: Microsoft Reserved Partition (for Windows).

Subcommands	Description
parted /dev/sda	Start Interactive Mode
parted /dev/sda print	Displays the partition table
parted /dev/sda mklabel gpt	Create a new disklabel. Common labels are gpt and msdos.
parted /dev/sda mkpart part_name 1MiB 10GiB	Create a New Partition.
parted /dev/sda mkpart part_name ext4 1MiB 10GiB	Create a New Partition with filesystem.
parted /dev/sda name part_num part_name	Assigns a name to a partition
parted /dev/sda resizepart 1 15GiB	Resize a Partition
pparted /dev/sdX set part_num lvm on/off	Set a flags
parted /dev/sda rm 1	Delete a Partition

Lab: Create new parition

• Assign label

# sda is the new disk
lsblk
# NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
# sda             8:0    0    1G  0 disk
# nvme0n1       259:0    0   20G  0 disk
# ├─nvme0n1p1   259:1    0  600M  0 part /boot/efi
# ├─nvme0n1p2   259:2    0    1G  0 part /boot
# └─nvme0n1p3   259:3    0 18.4G  0 part
#   ├─rhel-root 253:0    0 16.4G  0 lvm  /
#   └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]

# view the current partition, error: unrecognised disk label
parted sda print
# Error: /dev/sda: unrecognised disk label
# Model: ATA VMware Virtual S (scsi)
# Disk /dev/sda: 1074MB
# Sector size (logical/physical): 512B/512B
# Partition Table: unknown
# Disk Flags:

# assign label
parted /dev/sda mklabel msdos
# Information: You may need to update /etc/fstab

# Confirm
parted /dev/sda print
# Model: ATA VMware Virtual S (scsi)
# Disk /dev/sda: 1074MB
# Sector size (logical/physical): 512B/512B
# Partition Table: msdos
# Disk Flags:

# Number  Start  End  Size  Type  File system  Flags

• Create primary partition with a size of 100mb

parted /dev/sda mkpart primary 1mb 101mb
# Information: You may need to update /etc/fstab.

# confirm
parted /dev/sda print
# Model: ATA VMware Virtual S (scsi)
# Disk /dev/sda: 1074MB
# Sector size (logical/physical): 512B/512B
# Partition Table: msdos
# Disk Flags:

# Number  Start   End    Size    Type     File system  Flags
#  1      1049kB  101MB  99.6MB  primary

lsblk
# NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
# sda             8:0    0    1G  0 disk

• Delete a partition

# display table before deleting
parted /dev/sda print
# Model: ATA VMware Virtual S (scsi)
# Disk /dev/sda: 1074MB
# Sector size (logical/physical): 512B/512B
# Partition Table: msdos
# Disk Flags:

# Number  Start   End    Size    Type     File system  Flags
#  1      1049kB  101MB  99.6MB  primary

# delete
parted /dev/sda rm 1
# Information: You may need to update /etc/fstab.

# confirm
parted /dev/sda print
# Model: ATA VMware Virtual S (scsi)
# Disk /dev/sda: 1074MB
# Sector size (logical/physical): 512B/512B
# Partition Table: msdos
# Disk Flags:

# Number  Start  End  Size  Type  File system  Flags

---

fdisk: Manage Partitions

• fdisk

  • disk partitioning tool used to create, modify, delete, and manage partitions on a disk.

• Precautions

  • Data Loss:
    • Modifying partitions can result in data loss. Always back up important data before using fdisk.
  • Check Disk Details:
    • Use lsblk or fdisk -l to verify the correct device before making changes.
  • Partition Table Updates:
    • Changes take effect only after writing (w) in fdisk.

CMD	DESC
lsblk	Display block devices and their partitions in a tree view.
lsblk -f	Display partitions with file system type.
blkid	Display UUIDs and file system types for all partitions.
fdisk -l	Display details for all disks
fdisk -l /dev/sda	View partition details of a specific disk
fdisk /dev/sda	Open a specific disk for editing in Interactive Mode
parted /dev/sdX	Open a specific disk for editing in Interactive Mode
parted /dev/sdX resizepart 1 5GiB	Resize a Partition

• fdisk Interactive Mode Commands

Command	Description
m	Display a list of available commands.
p	Display the current partition table.
n	Create a new partition.
d	Delete an existing partition.
t	Change the type of a partition.
w	Write changes to the disk.
q	Quit without saving changes.

---

mkfs: Format a partition

• mkfs

  • used to create and format a filesystem on a storage device or partition

• Supported Filesystems

CMD	filesystem
mkfs.ext4	ext4
mkfs.xfs	xfs
mkfs.vfat	FAT32 (for compatibility with Windows).
mkfs.ntfs	NTFS (requires the ntfs-3g package).
mkfs.btrfs	Btrfs

• Common Commands

CMD	DESC
mkfs -t xfs /dev/sdb1	Specify the type of filesystem to create
mkfs.ext4 -L mydata /dev/sdb1	Label the Filesystem
mkfs.ext4 -b 4096 /dev/sdb1	Specify Block Size
mkfs.ext4 -v /dev/sdb1	Display detailed information during filesystem creation
mkfs.ext4 -c /dev/sdb1	Check for Bad Blocks

---

mount: Attach a Filesystem

• mount

  • attaches a filesystem to a directory (the mount point) in the Linux file hierarchy.
  • Once mounted, the data stored on the device can be accessed as part of the Linux filesystem.

• umount

  • detaches a mounted filesystem from the directory structure, ensuring no processes are using it.

• mount point

  • a directory or file that makes a new file system, directory, or file accessible.

CMD	DESC
mount	View All Mounted Filesystems
mount -a	Mount all filesystems mentioned in fstab
mount /dev/sdb1 /mnt	Mounts the partition /dev/sdb1 to the directory /mnt
mount -t ext4 /dev/sdb1 /mnt	Mount a Filesystem with a Specific Type
mount -o ro /dev/sdb1 /mnt	Mounts the partition as read-only.
mount -o loop /path/to/file.iso /mnt	Temporary mounts an ISO file as a loopback device.
mount /mnt	Mount a Filesystem Using /etc/fstab
umount /mnt	Unmount Using Mount Point
umount /dev/sdb1	Unmount Using Device
umount -f /mnt	Forces the unmount if the filesystem is busy.
umount -l /mnt	Detaches the filesystem but waits for any pending processes

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Lab: Create and Attach a New Partition

Add the New Disk to the VM

• Scenario: running out of space, additional space is required
• For VM, add a 2GB new disk(IDE).

---

Identify the New Disk in Linux

lsblk
# NAME                   MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
# sda                      8:0    0   2G  0 disk
# nvme0n1                259:0    0  30G  0 disk
# ├─nvme0n1p1            259:1    0   1G  0 part /boot
# └─nvme0n1p2            259:2    0  29G  0 part
#   ├─rhel_rhelhost-root 253:0    0  26G  0 lvm  /
#   └─rhel_rhelhost-swap 253:1    0   3G  0 lvm  [SWAP]

fdisk -l
# Disk /dev/nvme0n1: 30 GiB, 32212254720 bytes, 62914560 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes
# Disklabel type: dos
# Disk identifier: 0xed2f4154

# Device         Boot   Start      End  Sectors Size Id Type
# /dev/nvme0n1p1 *       2048  2099199  2097152   1G 83 Linux
# /dev/nvme0n1p2      2099200 62914559 60815360  29G 8e Linux LVM


# Disk /dev/sda: 2 GiB, 2147483648 bytes, 4194304 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes


# Disk /dev/mapper/rhel_rhelhost-root: 26 GiB, 27913093120 bytes, 54517760 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes


# Disk /dev/mapper/rhel_rhelhost-swap: 3 GiB, 3221225472 bytes, 6291456 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes

Note: the /dev/sda is the new device.

---

Partition the New Disk

# Open fdisk for the New Disk in the interactive mode
fdisk /dev/sda
# Welcome to fdisk (util-linux 2.32.1).
# Changes will remain in memory only, until you decide to write them.
# Be careful before using the write command.

# Device does not contain a recognized partition table.
# Created a new DOS disklabel with disk identifier 0xca628ef4.

# Command (m for help):

# ---------------------------

# m for help
m
# Help:

#   DOS (MBR)
#    a   toggle a bootable flag
#    b   edit nested BSD disklabel
#    c   toggle the dos compatibility flag

#   Generic
#    d   delete a partition
#    F   list free unpartitioned space
#    l   list known partition types
#    n   add a new partition
#    p   print the partition table
#    t   change a partition type
#    v   verify the partition table
#    i   print information about a partition

#   Misc
#    m   print this menu
#    u   change display/entry units
#    x   extra functionality (experts only)

#   Script
#    I   load disk layout from sfdisk script file
#    O   dump disk layout to sfdisk script file

#   Save & Exit
#    w   write table to disk and exit
#    q   quit without saving changes

#   Create a new label
#    g   create a new empty GPT partition table
#    G   create a new empty SGI (IRIX) partition table
#    o   create a new empty DOS partition table
#    s   create a new empty Sun partition table


# Command (m for help):
# ---------------------------
# n   add a new partition
n
# Partition type
#    p   primary (0 primary, 0 extended, 4 free)
#    e   extended (container for logical partitions)
# ---------------------------
# p to create a primary partition
p
# Partition number (1-4, default 1):enter
# First sector (2048-4194303, default 2048):enter
# Last sector, +sectors or +size{K,M,G,T,P} (2048-4194303, default 4194303):enter
#
# Created a new partition 1 of type 'Linux' and of size 2 GiB.
# ---------------------------
# w   write table to disk and exit
w
# The partition table has been altered.
# Calling ioctl() to re-read partition table.
# Syncing disks.
# ---------------------------


# confirm
lsblk
# NAME                   MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
# sda                      8:0    0   2G  0 disk
# └─sda1                   8:1    0   2G  0 part
# nvme0n1                259:0    0  30G  0 disk
# ├─nvme0n1p1            259:1    0   1G  0 part /boot
# └─nvme0n1p2            259:2    0  29G  0 part
#   ├─rhel_rhelhost-root 253:0    0  26G  0 lvm  /
#   └─rhel_rhelhost-swap 253:1    0   3G  0 lvm  [SWAP]

fdisk -l
# Disk /dev/nvme0n1: 30 GiB, 32212254720 bytes, 62914560 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes
# Disklabel type: dos
# Disk identifier: 0xed2f4154

# Device         Boot   Start      End  Sectors Size Id Type
# /dev/nvme0n1p1 *       2048  2099199  2097152   1G 83 Linux
# /dev/nvme0n1p2      2099200 62914559 60815360  29G 8e Linux LVM


# Disk /dev/sda: 2 GiB, 2147483648 bytes, 4194304 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes
# Disklabel type: dos
# Disk identifier: 0xca628ef4

# Device     Boot Start     End Sectors Size Id Type
# /dev/sda1        2048 4194303 4192256   2G 83 Linux


# Disk /dev/mapper/rhel_rhelhost-root: 26 GiB, 27913093120 bytes, 54517760 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes


# Disk /dev/mapper/rhel_rhelhost-swap: 3 GiB, 3221225472 bytes, 6291456 sectors
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes

Note: a new partition sda1 has been created within the device sda

---

Create a Filesystem

# makes an XFS filesystem on the new device
mkfs.ext4 /dev/sda1
# mke2fs 1.45.6 (20-Mar-2020)
# Creating filesystem with 524032 4k blocks and 131072 inodes
# Filesystem UUID: a62ee1c5-9e09-48ed-8671-0723f8899601
# Superblock backups stored on blocks:
#         32768, 98304, 163840, 229376, 294912

# Allocating group tables: done
# Writing inode tables: done
# Creating journal (8192 blocks): done
# Writing superblocks and filesystem accounting information: done

---

Mount the New Partition

# Create a Mount Point
mkdir /data
ll -d /data
# drwxr-xr-x. 2 root root 6 Dec 19 20:25 /data

# Mount the Partition
mount /dev/sda1 /data

# confirm
df -h
# Filesystem                      Size  Used Avail Use% Mounted on
# devtmpfs                        1.8G     0  1.8G   0% /dev
# tmpfs                           1.8G     0  1.8G   0% /dev/shm
# tmpfs                           1.8G  9.5M  1.8G   1% /run
# tmpfs                           1.8G     0  1.8G   0% /sys/fs/cgroup
# /dev/mapper/rhel_rhelhost-root   26G  7.3G   19G  28% /
# /dev/nvme0n1p1                 1014M  362M  653M  36% /boot
# tmpfs                           364M   12K  364M   1% /run/user/42
# tmpfs                           364M  4.0K  364M   1% /run/user/1001
# /dev/sda1                       2.0G   24K  1.9G   1% /data

Note: partition /dev/sda1 has been mounted on the /data

---

Persist the Mount in /etc/fstab

• Edit /etc/fstab

# Edit /etc/fstab
# add an entry for the new partition
vi /etc/fstab
# append the entry
# partition         mount point   fs type
# /dev/sda1         /data         ext4         defaults      0       0


# Test the /etc/fstab configuration without rebooting:
mount -a

• Reboot to verify

# reboot and confirm
reboot

df -h
# Filesystem                      Size  Used Avail Use% Mounted on
# devtmpfs                        1.8G     0  1.8G   0% /dev
# tmpfs                           1.8G     0  1.8G   0% /dev/shm
# tmpfs                           1.8G  9.6M  1.8G   1% /run
# tmpfs                           1.8G     0  1.8G   0% /sys/fs/cgroup
# /dev/mapper/rhel_rhelhost-root   26G  7.3G   19G  28% /
# /dev/nvme0n1p1                 1014M  362M  653M  36% /boot
# /dev/sda1                       2.0G   24K  1.9G   1% /data
# tmpfs                           364M   12K  364M   1% /run/user/42
# tmpfs                           364M  4.0K  364M   1% /run/user/1001

---

Lab: Unmount an Existing Partition

• Unmount /dev/sda1

su -

df -h
# Filesystem                      Size  Used Avail Use% Mounted on
# devtmpfs                        1.8G     0  1.8G   0% /dev
# tmpfs                           1.8G     0  1.8G   0% /dev/shm
# tmpfs                           1.8G  9.6M  1.8G   1% /run
# tmpfs                           1.8G     0  1.8G   0% /sys/fs/cgroup
# /dev/mapper/rhel_rhelhost-root   26G  7.3G   19G  28% /
# /dev/nvme0n1p1                 1014M  362M  653M  36% /boot
# /dev/sda1                       2.0G   24K  1.9G   1% /data
# tmpfs                           364M   12K  364M   1% /run/user/42
# tmpfs                           364M  4.0K  364M   1% /run/user/1001

# unmount a partition from a mount point
umount /data

# confirm
df -h
# Filesystem                      Size  Used Avail Use% Mounted on
# devtmpfs                        1.8G     0  1.8G   0% /dev
# tmpfs                           1.8G     0  1.8G   0% /dev/shm
# tmpfs                           1.8G  9.5M  1.8G   1% /run
# tmpfs                           1.8G     0  1.8G   0% /sys/fs/cgroup
# /dev/mapper/rhel_rhelhost-root   26G  7.3G   19G  28% /
# /dev/nvme0n1p1                 1014M  362M  653M  36% /boot
# tmpfs                           364M   12K  364M   1% /run/user/42
# tmpfs                           364M  4.0K  364M   1% /run/user/1001

---

Lab: Mount all partition mentioned in /etc/fstab

df -h
# Filesystem                      Size  Used Avail Use% Mounted on
# devtmpfs                        1.8G     0  1.8G   0% /dev
# tmpfs                           1.8G     0  1.8G   0% /dev/shm
# tmpfs                           1.8G  9.5M  1.8G   1% /run
# tmpfs                           1.8G     0  1.8G   0% /sys/fs/cgroup
# /dev/mapper/rhel_rhelhost-root   26G  7.3G   19G  28% /
# /dev/nvme0n1p1                 1014M  362M  653M  36% /boot
# tmpfs                           364M   12K  364M   1% /run/user/42
# tmpfs                           364M  4.0K  364M   1% /run/user/1001

#  mount all
mount -a

# confirm
df -h
# Filesystem                      Size  Used Avail Use% Mounted on
# devtmpfs                        1.8G     0  1.8G   0% /dev
# tmpfs                           1.8G     0  1.8G   0% /dev/shm
# tmpfs                           1.8G  9.5M  1.8G   1% /run
# tmpfs                           1.8G     0  1.8G   0% /sys/fs/cgroup
# /dev/mapper/rhel_rhelhost-root   26G  7.3G   19G  28% /
# /dev/nvme0n1p1                 1014M  362M  653M  36% /boot
# tmpfs                           364M   12K  364M   1% /run/user/42
# tmpfs                           364M  4.0K  364M   1% /run/user/1001
# /dev/sda1                       2.0G   24K  1.9G   1% /data

---