__Include: Manually Mounting a New Disk Device on Linux

This is an example of how to mount (and if necessary partition) an additional disk on a Charon host system. Please refer to the Linux manual pages for details.

The general tasks on the Charon host system require to identify the disk, add a file system to it (if this has not been done before), and mount the disk on a suitable mount-point.

Please note: the different cloud environments may offer the disk volumes to the Linux instance using different names. However, the basic steps will be the same as in the examples below.

Step 1: Identify new disk

After logging in on the system, you can identify the new disk using the lsblk command:

# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0   20G  0 disk 
├─sda1   8:1    0  200M  0 part /boot/efi
└─sda2   8:2    0 19,8G  0 part /
sdb      8:16   0  200G  0 disk 

In the example above, the new disk is /dev/sdb. The output shows no mount-point, i.e., the disk is not mounted yet. It also does not have any partitions.

Please note:

• A disk without partitions can also have a filesystem and data on it. Hence be sure that the disk really does not have any important data on it before you partition it.
• If a system has many disks, it is helpful to run the lsblk command before the new disk is added. This makes it easy to identify the new disk in the output after it has been added.

Step 2: Partition disk (fdisk or parted) - only if required

Please note: This step is only meant for new disks or to re-partition an existing disk. It will destroy all data on an existing disk.

Please refer to the manual pages ($ man parted and $ man fdisk) of your Linux distribution for details on the disk-partitioning commands. If the whole disk is used for one filesystem, it is not strictly required to create a partition. The decision of which disk layout is required depends on the customer requirements is the responsibility of the user.

After creating one partition on disk with fdisk (# fdisk /dev/sdb), the lsblk output shows the new partition:

# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0   30G  0 disk
├─sda1   8:1    0  500M  0 part /boot
└─sda2   8:2    0 29,5G  0 part /
sdb      8:32   0   64G  0 disk
└─sdb1   8:33   0   64G  0 part

Step3: Create a filesystem on the new partition(s)

Use the mkfs command to create a new filesystem. The selection of a filesystem depends on customer requirements. For example, to create an XFS filesystem, use

# mkfs.xfs /dev/sdb1

Please refer to the documentation of your Linux distribution for details about the mkfs command.

Step 4: Create a mount-point and mount the new filesystem

The following example shows how to create a mount-point and mount the file system.
To keep the example consistent with the sample outputs above, /dev/sdb1 is used in this example. However, as the /dev/sdX device names are not guaranteed to be persistent across reboots, it is strongly recommended to use names from the /dev/disk/by-* hierarchy (for example by-uuid) for permanent, production use.

# mkdir /space
# mount /dev/sdb1 /space

The df command shows the mounted filesystem:

# df
Filesystem     1K-blocks    Used Available Use% Mounted on
devtmpfs         4065684       0   4065684   0% /dev
tmpfs            4077556      16   4077540   1% /dev/shm
tmpfs            4077556    9224   4068332   1% /run
tmpfs            4077556       0   4077556   0% /sys/fs/cgroup
/dev/sda2       30929148 1677416  29251732   6% /
/dev/sda1         508580   65512    443068  13% /boot
tmpfs             815512       0    815512   0% /run/user/1000
/dev/sdb1       65923628   53272  62498580   1% /space

Step 5: Mount the disk automatically at system boot

To mount the disk automatically when the system boots, you must add it to the file /etc/fstab.

Please note: The device naming /dev/sdXN (e.g., /dev/sdb1) is not guaranteed to be persistent across reboots. Hence, it is advisable to use a persistent name from the /dev/disk/by* hierarchy (for example, the UUID).

You can use the ls or the blkid command to identify the UUID. Examples:

$ ls -l /dev/disk/by-uuid/
total 0
lrwxrwxrwx. 1 root root 10 2020-08-14 21:14 0c523909-fb78-48cb-9dc8-e7a08197a673 -> ../../dm-4
lrwxrwxrwx. 1 root root 10 2020-08-14 21:14 31fa8e8c-a6c0-45f7-9892-da13ba81e0e5 -> ../../sdb1

$ blkid |grep sdb1
/dev/sdb1: UUID="31fa8e8c-a6c0-45f7-9892-da13ba81e0e5" BLOCK_SIZE="4096" TYPE="xfs" PARTUUID="db62deaa-f25f-43d4-b958-700c1c13d844"

To add the device to /etc/fstab perform the following steps:

1. As the root user, open the file /etc/fstab with a text editor.
2. Add the mount command to the file. Please note: The following is for illustration only. The exact options depend on your requirements.
   Sample fstab entry:
   UUID=31fa8e8c-a6c0-45f7-9892-da13ba81e0e5 /space xfs defaults 1 2
3. Save the file.
4. Test if the automatic mount works correctly.