# SD card

***Copyright © Quectel Wireless Solutions Co., Ltd. 2026. All rights reserved.***

---

The **SD** card (**Secure Digital Card**) is a widely used portable storage medium, featuring small size, large capacity, low power consumption, and ease of use. It is commonly used in mobile phones, cameras, embedded devices, and single-board computers to store system files, applications, and data. It is one of the most mainstream storage solutions in modern mobile and embedded devices.

## Hardware Interface

The **Quectel Pi M1/L1** smart controller board is equipped with a **micro SD + Nano SIM** combo card slot, supporting the **SD 3.0** protocol.  
Note: The upper slot is the **micro SD** slot, and the lower slot is the **Nano SIM** slot.

```{image} images/image_NKbhbscINoGUjExRSWEcajH2n4b.webp
:width: 600px
:height: 370px
:align: center
```

## Function Usage

### System Detection

After inserting the **SD** card, use the following command to check whether the system has detected the device:

```bash
fdisk -l
```

By comparing the output before and after inserting the SD card, you can see that the system has successfully detected the SD card:

```{image} images/image_K9UTbYi2lodWmXxIKO2c3i22nOf.webp
:width: 600px
:height: 262px
:align: center
```

### Mount and Unmount

Check the mount path:

```bash
df -h
```

As shown below, the device is automatically mounted to `/mnt/sdcard`:

```{image} images/image_AeDNbuApyowYDpx8WvFc6y55nvb.webp
:width: 600px
:height: 385px
:align: center
```

List files in the mount directory:

```bash
ls /mnt/sdcard
```

Mount to another directory:

```bash
sudo mkdir -p /media/sdcard
sudo mount /dev/mmcblk1p1 /media/sdcard
```

Check the mount result:

```bash
ls /media/sdcard
```

Unmount when done:

```bash
sudo umount /media/sdcard
```

> Tip: Unmount the SD card before removing it to prevent data corruption.

### File Operations and Permissions

When a normal user accesses the **SD** card, permission issues may occur. Change the ownership of the mount point with the following commands:

```bash
sudo chown <username> /mnt/sdcard
sudo chmod 755 /mnt/sdcard
```

Replace ``<username>`` with your current login username. After that, you can read and write files normally in `/mnt/sdcard`.