> ## Documentation Index
> Fetch the complete documentation index at: https://dragonwingdocs.qualcomm.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Manage UEFI environment variables using the efivar tool

The `efivar` tool manages unified extensible firmware interface (UEFI) environment variables stored in the non-volatile firmware storage. Use these variables to configure the UEFI firmware and its environment.

The `efivars` are key-value pairs stored in the UEFI firmware. They hold settings for boot configuration, system state, and other essential parameters. The efivars manage boot entries and firmware settings, ensuring the system boots correctly and maintains its configuration.

To interact with the UEFI environment variables, use the following command:

```text theme={null}
efivar [-n name] [-f file] [-p] [-w]
```

Command options:

* `-n name`: Specify the name of the UEFI variable.
* `-f file`: Load or save variable contents from a file.
* `-p`: Print the value of the specified UEFI variable.
* `-w`: Write to the specified UEFI variable.

## **Update the** `OsIndications `**variable**

To update the `OsIndications` variable and verify the value of the EFI variable, do the following:

1. Create a `data.hex` file containing a specific byte sequence `04 00 00 00 00 00 00 00`.
   ```text theme={null}
   echo -e -n "\x4\x0\x0\x0\x0\x0\x0\x0" > data.hex
   ```
2. Write the contents of `data.hex` to the EFI variable `8be4df61-93ca-11d2-aa0d-00e098032b8c-OsIndications`.
   ```text theme={null}
   efivar -n 8be4df61-93ca-11d2-aa0d-00e098032b8c-OsIndications -f data.hex -w
   ```
3. To verify the value of the EFI variable `8be4df61-93ca-11d2-aa0d-00e098032b8c-OsIndications`, run the following command:
   ```text theme={null}
   efivar -n 8be4df61-93ca-11d2-aa0d-00e098032b8c-OsIndications -p
   ```
   Output of the previous command:
   ```text theme={null}
   GUID: 8be4df61-93ca-11d2-aa0d-00e098032b8c
   Name: "OsIndications"
   Attributes:
         Non-Volatile
         Boot Service Access
         Runtime Service Access
   Value:
   00000000  04 00 00 00 00 00 00 00
   ```

## **Update the** `VendorDtbOverlays `**variable**

To update the `VendorDtbOverlays` variable and verify the value of the EFI variable, do the following:

1. Create a `/var/data` file containing data `camx`.
   ```text theme={null}
   echo -n "camx" > /var/data
   ```
2. Write the contents of `/var/data` to the EFI variable `882f8c2b-9646-435f-8de5-f208ff80c1bd-VendorDtbOverlays`.
   ```text theme={null}
   efivar -n 882f8c2b-9646-435f-8de5-f208ff80c1bd-VendorDtbOverlays -f /var/data -w
   ```
3. To verify the value of the EFI variable `882f8c2b-9646-435f-8de5-f208ff80c1bd-VendorDtbOverlays`, run the following command:
   ```text theme={null}
   efivar -n 882f8c2b-9646-435f-8de5-f208ff80c1bd-VendorDtbOverlays -p
   ```
   Output of the previous command:
   ```text theme={null}
   GUID: 882f8c2b-9646-435f-8de5-f208ff80c1bd
   Name: "VendorDtbOverlays"
   Attributes:
         Non-Volatile
         Boot Service Access
         Runtime Service Access
   Value:
   00000000  63 61 6d 78                                       |camx            |
   ```

## **Next steps**

For more information, see [efivars Manual](https://man.freebsd.org/cgi/man.cgi?query=efivar\&sektion=8).