Being able to add storage to an OpenWrt system can be a very valuable option, because of the usually limited amount of flash on embedded devices. Having ample storage for applications and other data can therefore greatly expand OpenWrt functionality. For example you can turn your device into a full NAS by adding a hard drive for storing media files. You can also add storage to increase the available storage for the root file system in an overlay configuration by employing extroot.
Before the system can find your device it has to be properly recognised, which is done by installing the correct drivers for the device. For most devices the connection will be through USB, so you first have to install USB support and then provide storage support over USB. Other devices are possible too, like SATA, IDE and flash memory cards, see sata.essentials, ide.essentials and cf.essentials, respectively. This article will assume that your storage device is already installed correctly with the correct drivers and ready for use.
After installing the drivers for a device, it has to be partitioned and formatted with a File system (e.g. ext4, FAT) before data can be addressed as files and mountedby the OS. The usual Linux tools can be used to achieve these tasks from within OpenWrt. Certain packages are necessary for specific file system support and other packages facilitate more advanced functionality. This article explains the specifics and caveats of working with storage devices in OpenWrt and provides examples.
Partitioning means to write a partition table to the device, which defines which parts of the available space on the device belongs to which partition, each of which can have its own file system. Most commonly used partition tables are the Master Boot Record (MBR) and the GUID Partition Table (GPT). The latter is more modern and supports larger disks and more partitions. A device can also be used without a partition table, in which case there is only one file system on the device.
You can partition your device before connecting it to your OpenWrt powered device (e.g. on a PC), which may provide a wider range of options, like GPT support. You can then also format any partitions before attaching your device. However, there are packages in the OpenWrt repositories with which you can partition your devices:
fdiskis the standard tool to partition drives in Linux. for help with partitioning see TLDP)
cfdiskis a curses-based program for partitioning drives. Similar to fdisk, but provides a convenient menu based interface.
sfdiskis an alternative to list the size of a partition, list the partitions on a device, check the partitions on a device and repartition a device.
|All these utilities support MBR based partition tables only. Currently there are no tools in the default OPKG repository to create and partition GPT based devices. The Linux tools
Upon having your device partitioned, its partitions should be available as 'Device files' under
/dev/. For example
/dev/sda as the device, with
/dev/sda2, … , the partitions. Or, in case it is not partitioned with a partition table and it has a single file system, it may be directly accessible under e.g.
/dev/sda. Subsequent devices you add will be
/dev/sdc and so on. These 'device files' can now be partitioned (see below).
Available file systems and their packages can be listed with
opkg update; opkg list "kmod-fs*". These are kernel packages that provide necessary kernel support for reading and writing these file systems. The following table lists these file system kernel packages.
|kmod-fs-autofs4||Kernel module for AutoFS4 support|
|kmod-fs-btrfs||Kernel module for Btrfs support|
|kmod-fs-cifs||Kernel module for CIFS support|
|kmod-fs-exportfs||Kernel module for exportfs. Needed for some other modules.|
|kmod-fs-ext4||Kernel module for ext2, ext3 and ext4 filesystem support1)|
|kmod-fs-hfs||Kernel module for HFS filesystem support|
|kmod-fs-hfsplus||Kernel module for HFS+ filesystem support|
|kmod-fs-isofs||Kernel module for ISO9660 filesystem support|
|kmod-fs-minix||Kernel module for MINIX file system support|
|kmod-fs-msdos||Kernel module for MSDOS filesystem support|
|kmod-fs-nfs||Kernel module for NFS support|
|kmod-fs-nfs-common||Common NFS filesystem modules|
|kmod-fs-nfsd||Kernel module for NFS kernel server support|
|kmod-fs-ntfs||Kernel module for NTFS read only filesystem support|
|kmod-fs-reiserfs||Kernel module for ReiserFS support|
|kmod-fs-udf||Kernel module for UDF filesystem support|
|kmod-fs-vfat||Kernel module for VFAT filesystem support|
|kmod-fs-xfs||Kernel module for XFS support|
The choice of file system is dependent on several factors: performance, compatibility with other systems, functionality such as compression and journaling, security, etc. The remarks below are important to keep in mind when choosing your file system.
|✔||We recommend the file systems ext2, ext3, or ext4 (all supported by kmod-fs-ext4)|
|As of r26645 the modules for ext2 and ext3 (kmod-fs-ext2 and kmod-fs-ext3) are no longer available. You can use the module for ext4 kmod-fs-ext4 to mount ext2/ext3 as well, but then you have to mount your ext2 or ext3 partition like ext4 partition:
|If you are planning on sharing your USB storage with Samba, and/or using it to share large multimedia content over UPnP, e.g. with ushare, you should use ext3 or ext4 rather than ext2. Default Ext2 partitions will be limited to files of no more than 4 Gb, but this restriction is eliminated with the newer filesystems. To retain good performance with the newer filesystems, particularly on flash USB storage, you should also consider disabling journaling with the "
|With Ext2Fsd you obtain read/write access to ext2 ext3 and ext4 filesystems in Microsoft Windows. Native Linux file systems like ext2 or ext3 are the first choice when working with Linux. Don't bother with NTFS, VFAT and the like. They all have some quirks we could do without.|
|✘||We do NOT recommend using NTFS. While it is possible, it has serious performance issues under Linux.
If, for whatever reasons, you insist to utilize NTFS as file system, you may find Writable NTFS helpful.
For some filesystems, like for VFAT, you need to additionally install language packages (codepages / charsets) to handle the filenames. If your mount fails, look in dmesg - a message like
FAT: codepage cp437 not found
means that you need NLS codepage 437, and a message like
FAT: IO charset iso8859-1 not found
means that you need NLS ISO 8859-1.
***''kmod-nls-base''** Kernel module for NLS (Native Language Support)
Available NLS files and their packages can be listed with
opkg update; opkg list "kmod-nls*".
|kmod-nls-cp1250||Kernel module for NLS Codepage 1250 (Eastern Europe)|
|kmod-nls-cp1251||Kernel module for NLS Codepage 1251 (Russian)|
|kmod-nls-cp437||Kernel module for NLS Codepage 437 (United States, Canada)|
|kmod-nls-cp775||Kernel module for NLS Codepage 775 (Baltic Rim)|
|kmod-nls-cp850||Kernel module for NLS Codepage 850 (Europe)|
|kmod-nls-cp852||Kernel module for NLS Codepage 852 (Europe)|
|kmod-nls-cp866||Kernel module for NLS Codepage 866 (Cyrillic)|
|kmod-nls-iso8859-1||Kernel module for NLS ISO 8859-1 (Latin 1)|
|kmod-nls-iso8859-13||Kernel module for NLS ISO 8859-13 (Latin 7; Baltic)|
|kmod-nls-iso8859-15||Kernel module for NLS ISO 8859-15 (Latin 9)|
|kmod-nls-iso8859-2||Kernel module for NLS ISO 8859-2 (Latin 2)|
|kmod-nls-koi8r||Kernel module for NLS KOI8-R (Russian)|
|kmod-nls-utf8||Kernel module for NLS UTF-8|
The package e2fsprogs contains the essential ext2/3/4 filesystem utilities
tune2fs, and also most of the other core ext2/3/4 filesystem utilities available. For help with formatting see TLDP. Also see this page and the official page for more information on e2fsprogs.
As an example, for a device situated at
/dev/sda, to format its second partition
/dev/sda2 with the ext4 file system you can run
Note: When doing this, there will be no warning before execution and a new empty ext4 file system will be written to
/dev/sda2 immediately, using a quick format. Any data on the partition cannot be easily retrieved or is lost. Make sure that you enter the correct device file and partition as an argument for the formatting tool.
The file system checking utilities can be used in case the file system requires checking for errors.
Note: In order to perform a
e2fsck on 1 GiB partition, you will need at least 1 MiB of RAM.2) The same is true for
mke2fs. You can solve this by mounting a SWAP partition (or by using a device with enough RAM).
Note: In order to do
fsck (aka CHKDSK) of FAT32/VFAT partitions before mounting (i.e. during the boot process), you should read the following tickets:
Incorrect log output for mount point file systems without a fsck, and
Missing fsck function for block-mount/-hotplug of dos/vfat filesystems
There is no additional configuration needed for mounting your file system when the device is properly configured. Mounting works as is typical in Linux. Read the manual page for mount. Pay special attention to the options.
You can only mount a partition to an existing directory. You can create it with mkdir, for example:
mkdir -p /mnt/shares
To manually mount a partition, assuming that the second partition
/dev/sda2 on the device
/dev/sda is formatted with an ext4 file system, use:
mount -t ext4 /dev/sda2 /mnt/shares
The device can now be accessed at
/mnt/shares. Note that the
-t ext4 option is not strictly necessary as the file system is usually automatically detected.
To check if mounting was successful use
root@OpenWrt:~# df -h Filesystem Size Used Available Use% Mounted on rootfs 28.8M 4.5M 24.3M 16% / /dev/root 2.0M 2.0M 0 100% /rom tmpfs 61.8M 400.0K 61.4M 1% /tmp /dev/mtdblock5 28.8M 4.5M 24.3M 16% /overlay overlayfs:/overlay 28.8M 4.5M 24.3M 16% / tmpfs 512.0K 0 512.0K 0% /dev /dev/sda2 18.7G 67.6M 13.9G 0% /mnt/sharesThe device is listed here with its mount point in the last line. You can also run
mountwithout arguments to list all mount points.
To mount a swap partition, assuming that the first partition on the
/dev/sda device is linux swap space:
/dev/sda1 is not swap space yet, you can run
You can check swap functionality and status with the
free command. You can also check its status using
htop (installable package).
To unmount a swap partition:
It is convenient to be able to mount your file systems on boot. The package
block-mount will take care of this and also enable automatic mount when device is plugged in through use of ubox. As is typical in Linux, this is handled with Fstab Configuration. OpenWrt provides UCI configuration of Fstab. The configuration file is
For a technical background in which Fstab works, see block_mount. Note the information box below mentioning the new block-mount packages which works in conjunction with ubox.
Example settings in
fstab for mounting to
/mnt/share with automatic detection of the file system:
And to make the fstab settings effective in current session run:
To make the fstab settings effective after every reboot run:
Note: If you are having trouble with fstab, see fstab troubleshooting.
UCI CLI commands:
/etc/init.d/fstab stop uci add fstab mount uci set fstab.@mount[-1].device=/dev/sda1 uci set fstab.@mount[-1].options=rw,sync uci set fstab.@mount[-1].enabled_fsck=0 uci set fstab.@mount[-1].enabled=1 uci set fstab.@mount[-1].target=/mnt/share uci commit fstab /etc/init.d/fstab start
Delete with UCI CLI commands:
/etc/init.d/fstab stop uci delete fstab.@mount uci commit fstab /etc/init.d/fstab start
|In r26314 the three opkg packages
|2013-07-04: new block mount howto|
Once you successfully mounted your partition, you may want to install packages onto it. Please see Installation.Destination for that.
If you plan to install kernel modules on a USB drive you might want to read this: https://dev.openwrt.org/ticket/10739
An even better option might be to use extroot. This will allow you to use your device as a root, by using it in an overlay configuration over the original root.
If you have attached an external hard disk (e.g. through the USB port) and you don't use the disk all the time, you may want to spin down the disk after some time. One possible reason for this is to reduce the noise. A second reason is that some fanless external racks can get very hot and this is not healthy for the disk.
Unfortunately there is no solution that works always for everybody. The first option to try is provided by the package ''hd-idle'', which will spin down any disk accessible via the SCSI layer. Install it and test if it can spindown the hard disk (let us assume that your disk is
opkg install hd-idle hd-idle -t sdaIf you can hear the disk spins down, then you can configure the package, the configuration is in
hd-idle doesn't work, then the next option to try is hdparm:
opkg install hdparm hdparm -y /dev/sda
If you hear the disk spins down, then create a script
/etc/spindown with the following contents:
#!/bin/sh oldstate='' n="$2" while :; do sleep 60 newstate=$(grep "$1" /proc/diskstats) if [ "$newstate" = "$oldstate" ]; then n=$(($n - 1)) [ "$n" != 0 ] || hdparm -y /dev/"$1" else n="$2" oldstate=$newstate fi done &Then add to
/etc/rc.localthe following command (assuming your disk is
/dev/sdaand you want to spin it down after 20 minutes of inactivity):
/etc/spindown sda 20
The third option to try is the package
opkg install sdparm sdparm -f -C stop /dev/sdaIf you hear the disk spins down, use the script
/etc/spindownas in the case of hdparm, however replace the line
[ "$n" != 0 ] || hdparm -y /dev/"$1"with the line
[ "$n" != 0 ] || sdparm -f -C stop /dev/"$1"
Now let's do a virtual disk. You need an additional package.
opkg update opkg install kmod-fs-ext3 kmod-loop e2fsprogs insmod ext3 insmod loop
Then, create, and format the disk:
dd if=/dev/zero of=/mnt/hdd/owrt_loop bs=1M count=128 mke2fs -j -F -b 1024 /mnt/hdd/owrt_loop
To be able to use, plug-in for OpenWrt:
mkdir /mnt/loopdisk mount -o loop /mnt/hdd/owrt_loop /mnt/loopdisk
Now our system is not only the OpenWrt xMB, but x+128 MB
/etc/opkg.conf file into the following line
To install package:
opkg -dest usb install package
To delete package:
opkg -dest usb remove package
There are numerous things that go wrong with file systems not made for Linux. ext2, ext3 or ext4 file systems are therefore preferred.
Symptoms: You are trying to mount ext2 or ext3 partition and you have installed only kmod-fs-ext4. Neither
mount command nor
fstab works. The kmod-fs-ext4 issue definitely applies to Backfire, but is not an issue for Attitude Adjustment (tested on Attitude Adjustment RC1).
Solution a): you have to make sure that you are trying to mount the ext2 or ext3 partition like it was ext4 partition. Example /etc/config/fstab config and mount command follows:
mount -t ext4 /dev/sda1 /mnt -o rw,sync
Solution b): install
opkg update opkg install kmod-fs-ext3
This only applies to Backfire
swap-utilsThis package contains a collection of tools for managing swap space:
swapoff. This package exists, but swapon and swapoff seem to be just built into Busybox. Can someone explain this here?
blkidCommand-line utility to locate/print block device attributes.
ddA bit-stream duplicator to write directly to block devices.
Note: If you are having trouble using storage on a Huawei 3G dongle, you should read the following ticket:Mass storage missing from 3G dongle
doc/howto/storage.txt · Last modified: 2013/09/08 13:53 by grabbel