disk.md

Disk Management

• Linux
  • Detect New Disk
  • Create Partitions
  • Format the partition
  • Verify the new formatting
  • Mount the new volume by unchanging UUID for maximum stability
  • /tmp permissions
• Mac
• Meme
  • Backing Up Data

Linux

This example is from Adding a new EBS volume to a running AWS EC2 instance.

Detect New Disk

cat /proc/partitions

major minor  #blocks  name

 259        0  314572800 nvme0n1
 259        1       1024 nvme0n1p1
 259        2     204800 nvme0n1p2
 259        3     512000 nvme0n1p3
 259        4  313853935 nvme0n1p4
 259        5  524288000 nvme1n1  # <-- this is the new disk which has no partitions yet

If you can't see it yet, run partprobe

sudo partprobe

and then repeat the above cat /proc/partitions (it has also appeared after a few seconds on EC2 without this)

Create Partitions

You can create partitions using fdisk, gdisk or parted.

I prefer parted now because it's easier to script than fdisk, which I used to use interactively in the early to mid 2000s.

Create a new GPT partition table on the new disk:

sudo parted /dev/nvme1n1 --script mklabel gpt

Create a new partition that spans the entire disk:

sudo parted /dev/nvme1n1 --script mkpart primary 0% 100%

See the new partition:

cat /proc/partitions

...
 259        7  524285952 nvme1n1p1

Format the partition

Ext4:

sudo mkfs.ext4 /dev/nvme1n1p1

or

XFS:

sudo mkfs.xfs /dev/nvme1n1p1

Verify the new formatting

lsblk -f /dev/nvme1n1

or

sudo blkid /dev/nvme1n1p1

Mount the new volume by unchanging UUID for maximum stability

Since device numbers can change on rare occasion such as when adding IDE/SCSI/SAS disks to cables / disk controller cards shunting the ordering of device numbers, find and use the UUID instead using one of these commands:

I like this one best for scripting due to its simple 2 column output format which is easy to parse:

lsblk -o NAME,UUID

this one requires root permission:

sudo blkid

ls -l /dev/disk/by-uuid/

findmnt -o TARGET,UUID

requires root:

sudo fdisk -l

otherwise gets this error as regular user:

fdisk: cannot open /dev/nvme0n1: Permission denied

requires root or returns blank:

sudo parted -l

Add it to /etc/fstab with a line like this, substituting the UUID from the above commands:

UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx /tmp xfs defaults 0 2

If you're using a new mount point instead of /tmp that doesn't exist yet, then create it:

sudo mkdir -p /mnt/newdisk

If the mount point is /tmp make sure you shut down any processes that might be using it first like Informatica agent.

Then mount it using this short form of the mount command which tests the fstab at the same time:

sudo mount /tmp

mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

sudo systemctl daemon-reload

Check new mounted partition and space is available:

df -Th /tmp

Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/nvme1n1p1 xfs   500G  3.6G  497G   1% /tmp

/tmp permissions

If you've just mounted a new /tmp make sure to set a sticky bit and world writable permissions for people and apps to be able to use it:

sudo chmod 1777 /tmp

Mac

See Mac - Disk Management

Meme

Backing Up Data