---
title: "Mount a PFS on an instance"
description: "Mount a TIR Parallel File System on an instance, at creation or afterward, and know what each mount error means."
content_type: "how-to"
product: "tir-pfs"
platform: "TIR"
url: "/tir/tir-pfs/how-to/mount-a-pfs-on-an-instance/"
topic: ["create-and-connect"]
---

# Mount a PFS on an instance

Mount a PFS on an instance at a path you choose, either read-write or read-only.

## Before you begin

- A PFS in status **OK**, ready to mount; see
  [Create a PFS](/tir/tir-pfs/how-to/create-a-pfs/).
- An instance in the same project as the PFS. See
  [Create an instance](/tir/tir-instance/how-to/create-an-instance/).

## Mount a PFS when you create an instance

On the **Create Instance** form, open **Storage** > **Other storage**, pick a **Parallel File
System**, and give it a mount path. See [Create an
instance](/tir/tir-instance/how-to/create-an-instance/) and [Mount datasets and file
systems](/tir/tir-instance/how-to/mount-datasets-and-file-systems/#mount-storage-when-you-create-an-instance)
for every field on that form.

## Mount a PFS on an existing instance

1. Open the instance's page and select the **Parallel File-System** tab. It lists the project's PFS
   with their mount status and mount path.
2. In the PFS's row, type a mount path. To mount it read-only, tick **Read Only**; leave it clear to
   mount the PFS read-write.
3. Select **Mount**. The **Mounting PFS** dialog reminds you that mounting restarts the instance
   and that you will need to reinstall any packages you installed by hand. Tick the box to confirm,
   then select **Continue**.

To unmount, select **Unmount** in the PFS's row and confirm the **Unmounting PFS** dialog the same
way. Mounting or unmounting a PFS restarts a running instance.

Several instances can mount the same PFS at once, each read-write or read-only. For the full mount
path rules and how to check the mount worked, see [Mount datasets and file
systems](/tir/tir-instance/how-to/mount-datasets-and-file-systems/).

Each mount needs its own path, unique among the SFS and PFS on that instance. TIR also refuses a
second mount of a PFS that is already mounted on the instance, and an unmount of one that is already
unmounted. For the exact
messages and other errors, see [Troubleshooting TIR Parallel File
System](/tir/tir-pfs/troubleshooting/tir-pfs/).

## Check the mount

On the **Parallel File-System** tab, the PFS's **Mount Status** reads **Mounted**, with its **Mount
Path**. To see every instance that has a PFS mounted, see [See what uses a
PFS](/tir/tir-pfs/how-to/see-what-uses-a-pfs/).

## Access and permissions

On a container instance, root has full read and write access to a mounted PFS. To let another user
work with the PFS, create that user inside the container with a UID and GID between 1000 and 1050.

The PFS refuses a user outside that range, even when the file's own permissions would allow access.
Standard Linux owner, group, and other permissions still apply on top of this rule, so set a file
or directory's ownership to match the user that needs it.

To give several container users the same access, put them in one group with a GID between 1000 and
1050, and set the shared directory's group to that group. Check permissions after mounting to
confirm access works as you expect.

On a VM-based instance, any user can read or write a mounted PFS according to the file or
directory's own owner, group, and other permissions. The UID and GID range applies only inside a
container.

When you need more space, [increase the PFS's
size](/tir/tir-pfs/how-to/increase-the-size-of-a-pfs/), or [mount it on a
training cluster](/tir/tir-pfs/how-to/mount-a-pfs-on-a-training-cluster/) as well.