Site Tools


USB formatting with swap partition

A swap partition can prevent several types of insufficient RAM symptoms, such as system instability, failing processes, and in very severe cases, even spontaneous reboots. All this will depend largely on the network load and on FreshTomato's configuration. Some functions require much more RAM than others, and higher network traffic will put more load on the router and require more RAM than lower traffic. USB storage is an excellent way of providing swap space.

This example assumes you are using either an ARM or MIPS build with USB support. It is also assumes that you have already have USB support enabled. If you're not sure how to enable USB support, check the USB Support wiki page.

For this example, we used a 16GB USB flash drive which is seen in the system as device sda.

VERY IMPORTANT! The filesystem you're going to be choosing must support symbolic-links e.g. exfat(vfat) doesn't so entware will not work on it.

Automatic method

This assumes your drive device device name is sda ! If it's not, make sure to change the following commands consistent with your drive's device name.

The echo 1000M statement below defines the size of the swap partition (in MB). You may want to adjust that, according to your needs.

Then enter:

nvram set usb_automount="0"
(echo o; echo n; echo p; echo 2; echo ; echo +1000M; echo t; echo 82; echo n; echo p; echo 1; echo ; echo ; echo w) | fdisk $device
mkfs.ext2 -L usb $partion
mkswap -L swap $swappartion
swapon swap
mkdir /mnt/usb && mount /dev/sda1 /mnt/usb
nvram set usb_automount="1"

Manual method:

From the Web interface, disable the Automount checkbox in the USB Support menu.

Then, logon via SSH or Telnet and delete any existing partitions:

fdisk /dev/sda


At this point your USB flash drive is unpartitioned. Now let's create the necessary partition table:





+1000M (Essentially 1 GB will used for swap)






l (to verify)

w (write to save changes and exit fdisk)

At this point you should have two unformatted partitions on your USB flash drive:

sda1 ~14GB (fs-type ext2/3/4)
sda2 ~1GB (fs-type swap)

Now, let's format the partitions. The ext2 filesystem is recommended for USB flash drives and ext3 for hard disks/SSDs.

mkfs.ext2 -L usb /dev/sda1
mkswap -L swap /dev/sda2

Now, mount the partitions:

swapon swap
mkdir /mnt/usb && mount /dev/sda1 /mnt/usb

You can now re-enable USB Automount on the USB and NAS menu.

Final setup

The USB flash drive is now formatted. Your USB and NAS page settings should look like this:

Under Attached Devices, you should see something similar to this:

To verify the swap partition works properly, check the Overview menu. You should see information related to swap space:

usb_formatting_with_swap_partition.txt · Last modified: 2022/01/05 06:17 by rs232