Once you have obtained Basic USB support, you may want to connect a USB storage device to your router, for example a USB stick, a USB hard disk, etc. This article will tell you the steps and requirements to do this.
Note that this article is mainly about adding external space in addition to the internal flash usage. Moving the root-fs to an external storage space is described in the article extroot.
The main course of action is as follows:
/dev/. For example
/dev/sdaas 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/sdcand so on. Make sure that the file system requirements are satisfied by installing the proper kernel packages for specific file system support (see Storage);
When your USB device is properly recognised by the system, using the proper driver kernel packages listed in Basic USB support, the following packages facilitate USB storage support:
kmod-usb-storagerequired … Kernel support for USB Mass Storage devices.
kmod-fs-<file_system>required … the file system you formatted your partition in. Common examples include kmod-fs-ext4, kmod-fs-hfs, kmod-fs-hfsplus, kmod-fs-msdos, kmod-fs-ntfs, kmod-fs-reiserfs and kmod-fs-xfs.
kmod-usb-storage-extrasoptional … Kernel support for some more drivers, such as for SmartMedia card readers.
kmod-scsi-coreAny mass storage is a generic SCSI device.
| Before the Attitude Adjustment release, other optional packages included:
e2fsprogsadditional This package contains essential ext2/ext3/ext4 filesystem utilities for formatting and checking for errors on ext2/ext3/ext4 filesystems like mkfs.ext3, mkfs.ext4, fsck and other core utilities.
The following will install USB storage support, assuming USB works already, install ext4 file system support and mount a connected USB drive, pre-partitioned with a Linux swap partition and an ext4 partition.
opkg update opkg install kmod-usb-storage block-mount kmod-fs-ext4 mkswap /dev/sda1 swapon /dev/sda1 mkdir -p /mnt/share mount -t ext4 /dev/sda2 /mnt/share -o rw,sync
Note that partitions are usually auto detected, so this should work as well using default settings:
mount /dev/sda2 /mnt/share
Another example is how to use an external usb stick with a FAT32 partition (but we'll keep ext4 support also). See also Storage.
opkg update opkg install kmod-usb-storage block-mount block-hotplug kmod-fs-ext4 kmod-fs-vfat kmod-nls-cp437 kmod-nls-iso8859-1 mkdir -p /mnt/usb mount -t vfat /dev/sda1 /mnt/usb
You may create an empty file to indicate that the disk is not plugged in so that you don't put files directly onto NAND by doing
umount /mnt/usb #make sure the disk isn't mounted before doing this touch /mnt/usb/USB_DISK_NOT_PRESENT chmod 555 /mnt/usb chmod 444 /mnt/usb/USB_DISK_NOT_PRESENTThis will prevent only processes not running as root from writing onto NAND (see this discussion). You can of course also use this file in your own scripts.
The good news first: OpenWrt can use encrypted disks almost out-of-the-box.
The bad news is, there are some things to keep in mind.
Devices with 32 MB memory may run short of free memory. Symptoms can be that LUCI is displaying the Login page instead of the actual target page or that the out-of-memory killer starts killing tasks, so strange failures happen. Monitor the memory, e,g. using the
Decryption and encryption may slow down the system.
cryptsetup benchmark will show some numbers that can be compare for different platform. Unfortunately, only the hash algorithms work, the crypto algorithm tests currently (15.05, rampis) fail with
Required kernel crypto interface not available. Ensure you have algif_skcipher kernel module loaded.: find out why this fails and how to fix it. LUKS works fine, so it should work… See also the article about Cryptographic hardware accelerators for suggestions that may improve the situation. However, in the worst case there is too much load for the main core(s). Monitor the load, e,g. using the
uptimecommand, details of the output are explained in this article
Using Linux hard disk encryption with LUKS is straight forward:
opkg install cryptsetup lvm2 kmod-crypto-aes kmod-crypto-misc kmod-crypto-xts kmod-crypto-iv kmod-crypto-cbc kmod-crypto-hash kmod-dm
echo sha256_generic >/etc/modules.d/11-crypto-misc
cryptsetup luksOpen /dev/encrypted_partition usbstorage_luks && mount /dev/mapper/usbstorage_luks /mnt/mountpoint
umount /mnt/mountpoint && cryptsetup luksClose usbstorage_luks
Please refer to the existing documentations, e.g.