Oracle Cloud Infrastructure Documentation

Find Your Volume in the Instance

In Compute Cloud@Customer, when a block volume is initially attached to an instance, the instance sees the volume as a new disk, for example: as device /dev/sdb. This procedure describes how to list the disk devices in an instance so that you can find the volume and administer it in the OS.

For UNIX images, to mount these volumes when an instance boots, you need to add the volume to the /etc/fstab file. See Configuring Volumes to Automatically Mount (Linux Instances).

Optionally, you can perform various administrative tasks to configure the storage to suit your storage requirements.

The utilities you use to perform the administrative tasks vary depending on the type of OS in the instance. For more administrative information, refer to the documentation for the version of the OS that's on the instance. These documentation libraries provide access to helpful information:

Identifying the Boot Volume and the Attached Block Volume Devices in the Instance Using Linux Commands

  1. Log on to your instance. See Connecting to an Instance.

  2. List the disk devices.

    Important

    On UNIX OSs, the order in which volumes are attached is nondeterministic, so it can change with each reboot. If you refer to a volume using the device name, such as /dev/sdb, and you have more than one nonroot volume, there's no guarantee that the volume you intend to mount for a specific device name will be the volume mounted. When configuring the OS to recognize the block volume (for example, adding the volume to the /etc/fstab file), use the volume's SCSI ID as described in this procedure.

    sudo ls /dev/sd*
/dev/sda  /dev/sda1  /dev/sda2  /dev/sdb

    In this example, two devices are listed, /dev/sda and /dev/sdb.

  3. Use the fdisk -l command to view configuration information about the devices.

    In this example, /dev/sda is the boot volume and /dev/sdb is the attached block volume.

    sudo fdisk -l

Disk /dev/sda: 53.7 GB, 53687091200 bytes, 104857600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 8192 bytes / 8192 bytes
Disk label type: dos
Disk identifier: 0x000af694

   Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 61442047 29671424 8e Linux LVM

Disk /dev/mapper/ol-root: 27.2 GB, 27229421568 bytes, 53182464 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 8192 bytes / 8192 bytes


Disk /dev/mapper/ol-swap: 3145 MB, 3145728000 bytes, 6144000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 8192 bytes / 8192 bytes


Disk /dev/sdb: 1099.5 GB, 1099511627776 bytes, 2147483648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 8192 bytes / 8192 bytes

    This example output provides this information about /dev/sda and /dev/sdb:

    • The size of /dev/sda is 53.7 GB (boot volume).

    • /dev/sda has two partitions: /dev/sda1 and /dev/sda2.

    • The size of /dev/sdb is 1099.5 GB (the attached block volume), and doesn't have any partitions.

  4. Identify the devices that have file systems and are mounted in the OS. 

    sudo df -T
Filesystem          Type     1K-blocks    Used Available Use% Mounted on
devtmpfs            devtmpfs  16318164       0  16318164   0% /dev
tmpfs               tmpfs     16332596       0  16332596   0% /dev/shm
tmpfs               tmpfs     16332596    8744  16323852   1% /run
tmpfs               tmpfs     16332596       0  16332596   0% /sys/fs/cgroup
/dev/mapper/ol-root xfs       26578248 2907292  23670956  11% /
/dev/sda1           xfs        1038336  292512    745824  29% /boot
tmpfs               tmpfs      3266520       0   3266520   0% /run/user/0

    In this example:

    • /dev/sda1 has an xfs file system and it's mounted on /boot (the boot volume).

    • /dev/sdb isn't listed because this block volume was just attached and hasn't had a file system created and isn't mountable yet.

  5. Find the SCSI ID for the newly attached volume.

    sudo ls -l /dev/disk/by-id
total 0
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 dm-name-ol-root -> ../../dm-0
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 dm-name-ol-swap -> ../../dm-1
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 dm-uuid-LVM-83pr2aUrW2ZdCbWgsN4ZRFqvsXGGNZ8JO6il7j1YTWpywZeewYCiA6ywDmIeho1G -> ../../dm-0
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 dm-uuid-LVM-83pr2aUrW2ZdCbWgsN4ZRFqvsXGGNZ8JsaUihE3RWozk5u4p5nOwG9sFcj34AU3F -> ../../dm-1
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 lvm-pv-uuid-Dh9ydC-Rj90-chhj-tkwq-ZI0Z-mfop-Wtg5bh -> ../../sda2
lrwxrwxrwx. 1 root root  9 Dec  6 18:26 scsi-3600144f096933b92000061ae9bfc0025 -> ../../sda
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 scsi-3600144f096933b92000061ae9bfc0025-part1 -> ../../sda1
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 scsi-3600144f096933b92000061ae9bfc0025-part2 -> ../../sda2
lrwxrwxrwx. 1 root root  9 Dec  8 15:17 scsi-3600144f096933b92000061b1129e0037 -> ../../sdb
lrwxrwxrwx. 1 root root  9 Dec  6 18:26 wwn-0x600144f096933b92000061ae9bfc0025 -> ../../sda
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 wwn-0x600144f096933b92000061ae9bfc0025-part1 -> ../../sda1
lrwxrwxrwx. 1 root root 10 Dec  6 18:26 wwn-0x600144f096933b92000061ae9bfc0025-part2 -> ../../sda2
lrwxrwxrwx. 1 root root  9 Dec  8 15:17 wwn-0x600144f096933b92000061b1129e0037 -> ../../sdb

    In this example, the following line shows the SCSI ID assigned to sdb:

    lrwxrwxrwx. 1 root root 9 Dec 8 15:17 scsi-3600144f096933b92000061b1129e0037 -> ../../sdb

    where scsi-3600144f096933b92000061b1129e0037 is the SCSI ID.

    The SCSI ID is a persistent device name for /dev/sdb and is used when performing administrative operations on the device, such as partitioning, creating a file system, and mounting.

    For more information about mounting a block volume file system to an instance, see Configuring Volumes to Automatically Mount (Linux Instances).

  6. Perform administrative tasks to configure the block volume to suit your storage requirements.

    The specific tasks you perform depend on the type of OS that runs the instance and how you want the storage configured. Refer to your OS documentation for details.