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Linux
If you attached a new, blank disk to your VM, before you can use it you must
format and mount the disk. If you attached a disk that already contains data,
then you must mount the disk before you can use it.
Before you begin
If you haven't already, set up authentication.
Authentication verifies your identity for access to Google Cloud services and APIs. To run
code or samples from a local development environment, you can authenticate to
Compute Engine by selecting one of the following options:
Select the tab for how you plan to use the samples on this page:
Console
When you use the Google Cloud console to access Google Cloud services and
APIs, you don't need to set up authentication.
gcloud
Install the Google Cloud CLI.
After installation,
initialize the Google Cloud CLI by running the following command:
In this example, the new Persistent Disk was created with the name
extra-scsi-disk. The device name for the new disk is sdb.
Format the disk device using the
mkfs tool.
This command deletes all data from the specified disk, so make sure
that you specify the disk device correctly.
You can use any file format that you need, but we recommend a single
ext4 file system without a partition table. You can
increase the size of your disk
later without having to modify disk partitions.
To maximize disk performance, use the recommended formatting options
with the -E flag. It is not necessary to reserve space for the root
volume on this secondary disk, so specify -m 0 to use all of the
available disk space. The following command formats the entire disk with no
partition table.
FILE_SYSTEM_TYPE: the file system type. For example, ext2,
ext3, ext4, or xfs.
DEVICE_NAME: the device name of the
disk that you are formatting. For example, using the example output from
the first step, you would use sdb for the device name.
Mount the disk
Create a directory that serves as the mount point for the new disk on the VM.
You can use any directory. The following example creates a directory under
/mnt/disks/.
$ sudo mkdir -p /mnt/disks/MOUNT_DIR
Replace MOUNT_DIR with the directory at which to
mount disk.
Use the mount tool
to mount the disk to the instance, and enable the discard option:
$ sudo mount -o discard,defaults /dev/DEVICE_NAME /mnt/disks/MOUNT_DIR
Replace the following:
DEVICE_NAME: the device name of the disk to
mount.
MOUNT_DIR: the directory in which to mount
your disk.
Configure read and write permissions on the disk. For this example,
grant write access to the disk for all users.
$ sudo chmod a+w /mnt/disks/MOUNT_DIR
Replace MOUNT_DIR with the directory where you
mounted your disk.
Configure automatic mounting on VM restart
Add the disk to your /etc/fstab file, so that the disk automatically
mounts again when the VM restarts. On Linux operating systems, the
device name can change with each reboot, but the device UUID always points
to the same volume, even when you move disks between systems. Because of this,
we recommend using the device UUID instead of the device name to configure
automatic mounting on VM restart.
Create a backup of your current /etc/fstab file.
$ sudo cp /etc/fstab /etc/fstab.backup
Use the blkid command to list the UUID for the disk.
DEVICE_NAME: the device name of the disk that
you want to automatically mount. If you created a partition table on the
disk, specify the partition that you want to mount by adding the suffix
appended to the device name. For example, if sdb is the device name
for the disk, sdb1 might be the name for the partition.
Open the /etc/fstab file in a text editor and create an entry that
includes the UUID. For example:
UUID_VALUE: the UUID of the disk, listed in
the output of the previous step
MOUNT_DIR: the directory where you mounted
your disk
FILE_SYSTEM_TYPE: the file system type.
For example, ext2, ext3, ext4, or xfs.
MOUNT_OPTION: specifies what the operating
system does if it cannot mount the zonal persistent disk at boot time.
For valid values, see The fourth field in the Linux fstab
documentation.
To let the system boot even if the disk is unavailable, use the nofail
mount option.
Use the cat command to verify that your /etc/fstab entries are correct:
Always keep the /etc/fstab file in sync with the devices that are attached to
a VM. If you want to detach a disk or create a snapshot from the boot disk
for a VM, edit the /etc/fstab file and remove the entry for the disk. Even
if you set MOUNT_OPTION to nofail or nobootwait,
remove the entry before you create your boot disk snapshot or detach the disk.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-26 UTC."],[[["\u003cp\u003eNew or pre-existing disks attached to a Linux VM must be formatted and/or mounted before they can be used.\u003c/p\u003e\n"],["\u003cp\u003eFormatting a disk with the \u003ccode\u003emkfs\u003c/code\u003e tool deletes all data, requiring correct disk device specification, and \u003ccode\u003eext4\u003c/code\u003e is recommended for maximizing disk performance.\u003c/p\u003e\n"],["\u003cp\u003eMounting a disk involves creating a mount point directory and using the \u003ccode\u003emount\u003c/code\u003e tool, and you can set permissions such as universal write access using \u003ccode\u003echmod\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eTo ensure disks automatically mount on VM restart, you should add an entry to the \u003ccode\u003e/etc/fstab\u003c/code\u003e file using the disk's UUID instead of its device name.\u003c/p\u003e\n"],["\u003cp\u003eIt is crucial to keep the \u003ccode\u003e/etc/fstab\u003c/code\u003e file updated to match the current disk configuration and remove disk entries before detaching or snapshotting.\u003c/p\u003e\n"]]],[],null,["# Format and mount a non-boot disk on a Linux VM\n\nLinux\n\n*** ** * ** ***\n\nIf you attached a new, blank disk to your VM, before you can use it you must\nformat and mount the disk. If you attached a disk that already contains data,\nthen you must mount the disk before you can use it.\n\nBefore you begin\n----------------\n\n- If you haven't already, set up [authentication](/compute/docs/authentication). Authentication verifies your identity for access to Google Cloud services and APIs. To run code or samples from a local development environment, you can authenticate to Compute Engine by selecting one of the following options:\n\n Select the tab for how you plan to use the samples on this page: \n\n ### Console\n\n\n When you use the Google Cloud console to access Google Cloud services and\n APIs, you don't need to set up authentication.\n\n ### gcloud\n\n 1.\n [Install](/sdk/docs/install) the Google Cloud CLI.\n\n After installation,\n [initialize](/sdk/docs/initializing) the Google Cloud CLI by running the following command:\n\n ```bash\n gcloud init\n ```\n\n\n If you're using an external identity provider (IdP), you must first\n [sign in to the gcloud CLI with your federated identity](/iam/docs/workforce-log-in-gcloud).\n | **Note:** If you installed the gcloud CLI previously, make sure you have the latest version by running `gcloud components update`.\n 2. [Set a default region and zone](/compute/docs/gcloud-compute#set_default_zone_and_region_in_your_local_client).\n\n ### REST\n\n\n To use the REST API samples on this page in a local development environment, you use the\n credentials you provide to the gcloud CLI.\n 1. [Install](/sdk/docs/install) the Google Cloud CLI. After installation, [initialize](/sdk/docs/initializing) the Google Cloud CLI by running the following command: \n\n ```bash\n gcloud init\n ```\n 2. If you're using an external identity provider (IdP), you must first [sign in to the gcloud CLI with your federated identity](/iam/docs/workforce-log-in-gcloud).\n\n\n For more information, see\n [Authenticate for using REST](/docs/authentication/rest)\n in the Google Cloud authentication documentation.\n\nConnect to the VM\n-----------------\n\n1. Go to the **VM instances** page.\n\n [Go to the VM instances page](https://console.cloud.google.com/compute/instances)\n2. Click the **SSH** button next to the instance that has the new attached\n disk. The browser opens a terminal connection to the VM.\n\nFormat a non-boot disk on a Linux VM\n------------------------------------\n\n#### Permissions required for this task\n\nTo perform this task, you must have the following\n[permissions](/iam/docs/overview#permissions):\n\n\n- `compute.instances.setMetadata` on the instance, so that you can connect using SSH\n\n\u003cbr /\u003e\n\nIf you are connecting to a VM instance that can run as a service account,\nyou must also grant the `roles/iam.serviceAccountUser` role.\n\n1. In the terminal, use the [symlink](/compute/docs/disks/disk-symlinks)\n created for your attached disk to determine which device to format.\n\n ls -l /dev/disk/by-id/google-*\n\n Unformatted disks don't have additional symlinks with\n `-part`\u003cvar translate=\"no\"\u003eN\u003c/var\u003e in the name. \n\n google-extra-scsi-disk -\u003e ../../sdb\n google-instance-2 -\u003e ../../sda\n google-instance-2-part1 -\u003e ../../sda1\n google-instance-2-part14 -\u003e ../../sda14\n google-instance-2-part15 -\u003e ../../sda15\n google-local-nvme-ssd-0 -\u003e ../../nvme0n1\n google-local-nvme-ssd-1 -\u003e ../../nvme0n2\n\n In this example, the new Persistent Disk was created with the name\n `extra-scsi-disk`. The device name for the new disk is `sdb`.\n2. Format the disk device using the\n [`mkfs` tool](http://manpages.ubuntu.com/manpages/xenial/man8/mkfs.8.html).\n This command **deletes** all data from the specified disk, so make sure\n that you specify the disk device correctly.\n\n You can use any file format that you need, but we recommend a single\n `ext4` file system without a partition table. You can\n [increase the size of your disk](/compute/docs/disks/resize-persistent-disk)\n later without having to modify disk partitions.\n\n To maximize disk performance, use the [recommended formatting options](/compute/docs/disks/optimizing-pd-performance#formatting_parameters)\n with the `-E` flag. It is not necessary to reserve space for the root\n volume on this secondary disk, so specify `-m 0` to use all of the\n available disk space. The following command formats the entire disk with no\n partition table.\n\n \u003cbr /\u003e\n\n ```\n $ sudo mkfs.FILE_SYSTEM_TYPE -m 0 -E lazy_itable_init=0,lazy_journal_init=0,discard /dev/DEVICE_NAME\n \n ```\n\n \u003cbr /\u003e\n\n Replace the following:\n - \u003cvar translate=\"no\"\u003eFILE_SYSTEM_TYPE\u003c/var\u003e: the file system type. For example, `ext2`, `ext3`, `ext4`, or `xfs`.\n - \u003cvar translate=\"no\"\u003eDEVICE_NAME\u003c/var\u003e: the device name of the disk that you are formatting. For example, using the example output from the first step, you would use `sdb` for the device name.\n\nMount the disk\n--------------\n\n1. Create a directory that serves as the mount point for the new disk on the VM.\n You can use any directory. The following example creates a directory under\n `/mnt/disks/`.\n\n ```\n $ sudo mkdir -p /mnt/disks/MOUNT_DIR\n ```\n\n Replace \u003cvar translate=\"no\"\u003eMOUNT_DIR\u003c/var\u003e with the directory at which to\n mount disk.\n2. Use the [mount tool](http://manpages.ubuntu.com/manpages/xenial/man8/mount.8.html)\n to mount the disk to the instance, and enable the `discard` option:\n\n ```\n $ sudo mount -o discard,defaults /dev/DEVICE_NAME /mnt/disks/MOUNT_DIR\n ```\n\n Replace the following:\n - \u003cvar translate=\"no\"\u003eDEVICE_NAME\u003c/var\u003e: the device name of the disk to mount.\n - \u003cvar translate=\"no\"\u003eMOUNT_DIR\u003c/var\u003e: the directory in which to mount your disk.\n3. Configure read and write permissions on the disk. For this example,\n grant write access to the disk for all users.\n\n ```\n $ sudo chmod a+w /mnt/disks/MOUNT_DIR\n ```\n\n Replace \u003cvar translate=\"no\"\u003eMOUNT_DIR\u003c/var\u003e with the directory where you\n mounted your disk.\n\n### Configure automatic mounting on VM restart\n\nAdd the disk to your `/etc/fstab` file, so that the disk automatically\nmounts again when the VM restarts. On Linux operating systems, the\n*device name* can change with each reboot, but the *device UUID* always points\nto the same volume, even when you move disks between systems. Because of this,\nwe recommend using the device UUID instead of the device name to configure\nautomatic mounting on VM restart.\n| **Note:** If you use Container-Optimized OS, modifications to `/etc/fstab` don't persist across system reboots. To ensure the device is checked and mounted during boot, run the `fsck` and `mount` operations on the disk from your cloud-config's `bootcmd` section. See [Mounting and formatting\n| disks](/container-optimized-os/docs/concepts/disks-and-filesystem#mounting_and_formatting_disks) in the Container-Optimized OS documentation.\n\n1. Create a backup of your current `/etc/fstab` file.\n\n ```\n $ sudo cp /etc/fstab /etc/fstab.backup\n ```\n2. Use the `blkid` command to list the UUID for the disk.\n\n ```\n $ sudo blkid /dev/DEVICE_NAME\n ``` \n\n ```\n /dev/DEVICE_NAME: UUID=\"a9e1c14b-f06a-47eb-adb7-622226fee060\" BLOCK_SIZE=\"4096\"\n TYPE=\"ext4\" PARTUUID=\"593b3b75-108f-bd41-823d-b7e87d2a04d1\"\n ```\n\n Replace the following:\n - \u003cvar translate=\"no\"\u003eDEVICE_NAME\u003c/var\u003e: the device name of the disk that you want to automatically mount. If you created a partition table on the disk, specify the partition that you want to mount by adding the suffix appended to the device name. For example, if `sdb` is the device name for the disk, `sdb1` might be the name for the partition.\n3. Open the `/etc/fstab` file in a text editor and create an entry that\n includes the UUID. For example:\n\n ```\n UUID=UUID_VALUE /mnt/disks/MOUNT_DIR FILE_SYSTEM_TYPE discard,defaults,MOUNT_OPTION 0 2\n ```\n\n Replace the following:\n - \u003cvar translate=\"no\"\u003eUUID_VALUE\u003c/var\u003e: the UUID of the disk, listed in the output of the previous step\n - \u003cvar translate=\"no\"\u003eMOUNT_DIR\u003c/var\u003e: the directory where you mounted your disk\n - \u003cvar translate=\"no\"\u003eFILE_SYSTEM_TYPE\u003c/var\u003e: the file system type. For example, `ext2`, `ext3`, `ext4`, or `xfs`.\n - \u003cvar translate=\"no\"\u003eMOUNT_OPTION\u003c/var\u003e: specifies what the operating system does if it cannot mount the zonal persistent disk at boot time. For valid values, see **The fourth field** in the [Linux `fstab`\n documentation](https://man7.org/linux/man-pages/man5/fstab.5.html). To let the system boot even if the disk is unavailable, use the `nofail` mount option.\n4. Use the `cat` command to verify that your `/etc/fstab` entries are correct:\n\n ```\n $ cat /etc/fstab\n\n UUID=6B33-A686 /boot/efi vfat defaults 0 0\n UUID=\u003cvar translate=\"no\"\u003eUUID_VALUE\u003c/var\u003e /mnt/disks/\u003cvar translate=\"no\"\u003eMOUNT_DIR\u003c/var\u003e \u003cvar translate=\"no\"\u003eFILE_SYSTEM_TYPE\u003c/var\u003e discard,defaults,\u003cvar translate=\"no\"\u003eMOUNT_OPTION\u003c/var\u003e 0 2\n\n ```\n\nAlways keep the `/etc/fstab` file in sync with the devices that are attached to\na VM. If you want to detach a disk or create a snapshot from the boot disk\nfor a VM, edit the `/etc/fstab` file and remove the entry for the disk. Even\nif you set \u003cvar translate=\"no\"\u003eMOUNT_OPTION\u003c/var\u003e to `nofail` or `nobootwait`,\nremove the entry before you create your boot disk snapshot or detach the disk.\n\nWhat's next\n-----------\n\n- [Configure persistent device names](/compute/docs/disks/set-persistent-device-name-in-linux-vm) for your added disks.\n- Learn how to [resize your persistent disks](/compute/docs/disks/resize-persistent-disk).\n- Learn how to regularly [back up your disks using snapshots](/compute/docs/disks/create-snapshots) to prevent unintended data loss."]]
