The Basics

One of the first things you notice when using the GL.iNet MT1300 (Beryl) as more than a basic travel router is how fast you hit a wall:

14 MB free for configs, packages, logs, and plugins.

That’s not a bug — it’s how OpenWrt is designed on small embedded devices. The good news is that the MT1300 has a microSD slot, and OpenWrt has a battle-tested solution for this exact problem: extroot.

This post walks through a working, GL.iNet-compatible extroot setup that avoids the usual traps (NTFS/exFAT, late mounts, device-path failures).

The problem: why you only have ~14 MB

OpenWrt splits storage into layers:

/rom → read-only firmware
/overlay → writable space (configs, installed packages)
/ → union filesystem (rom + overlay)

On the MT1300, /overlay lives on internal flash:

/dev/mtdblock6  ≈ 15 MB

That space cannot be expanded internally. Installing VPNs, ad-blocking, download tools, or even logs quickly exhausts it.

The solution: extroot (overlay on SD card)

Extroot moves /overlay from internal flash to external storage.

After extroot:

Internal flash still boots the router
The SD card becomes /overlay
You gain GBs of writable space
The router behaves exactly the same

If the SD card is missing, OpenWrt safely falls back to the internal overlay.

Requirements

GL.iNet MT1300 (Beryl)
microSD card (8 GB+ recommended)
Filesystem: ext4
SSH access
Stock GL.iNet firmware (OpenWrt-based)

Step 1: Format the SD card as ext4

Extroot does not work with NTFS or exFAT.

Insert the SD card and SSH into the router:

ssh root@192.168.8.1

Unmount the card if it’s auto-mounted:

umount /mnt/mmcblk0p1 2>/dev/null

Format it:

mkfs.ext4 /dev/mmcblk0p1

⚠️ This wipes the card.

Step 2: Install required packages

opkg update
opkg install block-mount kmod-fs-ext4 e2fsprogs

Step 3: Generate a proper fstab (critical)

Instead of hard-coding /dev/mmcblk0p1, use OpenWrt’s block system so the SD mounts early enough during boot.

block detect > /etc/config/fstab

Edit the file:

vi /etc/config/fstab

You’ll see an entry similar to:

config mount
    option target '/mnt/mmcblk0p1'
    option uuid 'XXXX-XXXX'
    option fstype 'ext4'
    option enabled '1'

Step 4: Convert that entry into extroot

Change the block to:

config mount
    option target '/overlay'
    option uuid 'XXXX-XXXX'
    option fstype 'ext4'
    option enabled '1'
    option enabled_fsck '1'

Why UUID matters:
Device paths can change during early boot. UUID ensures the overlay mounts reliably before /overlay initializes.

Step 5: Copy your existing overlay

Mount the SD card temporarily:

mkdir -p /mnt/sd
mount /dev/mmcblk0p1 /mnt/sd

Copy everything from the current overlay (preserves permissions and symlinks):

tar -C /overlay -cvf - . | tar -C /mnt/sd -xvf -

Unmount it again:

umount /mnt/sd

Step 6: Enable fstab and reboot

/etc/init.d/fstab enable
reboot

Do not remove the SD card after this point.

Step 7: Verify success

After reboot, SSH back in and run:

df -h

What success looks like

/dev/mmcblk0p1   115G   200M   110G   /overlay
overlayfs:/overlay

What failure looks like

/dev/mtdblock6   15M    1M     14M    /overlay

If you see the second output, extroot didn’t activate (usually due to filesystem type or incorrect fstab entries).

Why this works

ext4 supports permissions, symlinks, and overlay semantics
block detect ensures the mount happens early
UUID-based mounting avoids race conditions at boot
The internal flash remains untouched and bootable

What this unlocks

With extroot enabled, the MT1300 can comfortably run:

AdGuard Home
aria2 / rtorrent
VPN stacks + extras
Samba / media storage
Heavy logging
Home Assistant helpers
“Travel server” setups

All without worrying about storage again.

Final notes

Use a reliable SD card (SanDisk / Samsung)
Avoid hot-removal after extroot is active
ext4 is non-negotiable
Journaled filesystem makes power loss safe for travel use

Escaping the 14 MB Trap: Expanding Storage on a GL.iNet MT1300 (Beryl) with Extroot