---
title: mdadm (multiple device administration) — Software RAID configuration and management
date: 2026-10-20
time: 12:00
model: admin
category: programs
author_type: human
summary: A tool for creating, growing and monitoring software RAID arrays with the Linux md driver.
tags: program, File and disk management, mdadm
---

A tool for creating, growing and monitoring software RAID arrays with the Linux md driver.

## Basic Information

| Command Name | mdadm (multiple device administration) |
| --- | --- |
| One-line Introduction | A tool for creating, growing and monitoring software RAID arrays with the Linux md driver. |
| Provided by | mdadm (distribution package) |
| Official Documentation | https://man7.org/linux/man-pages/man8/mdadm.8.html |
| Supported Operating Systems | Linux |
| Installation Status | Requires the mdadm package |
| Category | Linux file and disk management (tags: RAID, mdadm, mirroring, disk, recovery) |

## What is this command?

mdadm combines several block devices into RAID 0, 1, 5, 6 or 10 arrays. Array status appears in /proc/mdstat, and mirrors or parity keep data available when one disk fails.

Array metadata is stored in /etc/mdadm/mdadm.conf so it can be assembled at boot. After replacing a disk, use --add and --grow to rebuild and expand.

## What problems does it solve?

- You want to combine several disks into one volume
- You need a mirror that survives a disk failure
- You are replacing a failed disk and rebuilding
- You need array status and rebuild progress
## Key features

### Create an array

--create builds an array from a level and a device list.

- **When to use**: You are building a new RAID set
- **What you get**: An array device such as /dev/md0
- **Limitations**: Existing data on the devices is erased.
### Monitor status

--detail and /proc/mdstat show members and health.

- **When to use**: During routine checks or incident response
- **What you get**: Per-device state and rebuild progress
- **Limitations**: Without a monitoring daemon you get no alerts.
### Replace and grow

Mark a disk failed, remove it, add the new one, then grow if needed.

- **When to use**: Replacing a failed disk or adding capacity
- **What you get**: A rebuilt array with more capacity
- **Limitations**: Performance drops significantly during a rebuild.
## Installation and usage

### Check whether it is installed

```
mdadm --version
```

sudo apt install mdadm   # Debian/Ubuntu
sudo dnf install mdadm   # Fedora

## Real-world examples

### Create a RAID 1 mirror

Combine two devices into a mirrored array.

```
sudo mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1
```

### Check status

Show array details and kernel status.

```
sudo mdadm --detail /dev/md0
cat /proc/mdstat
```

### Save configuration

Record the array so it is assembled automatically at boot.

```
sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf
sudo update-initramfs -u
```

---
Source (HTML): https://games.aidebatehub.com/programs/linux/filesystem/mdadm.html
This file is an auto-generated Markdown twin of the DevHub document.