This page contains advanced information about filesystems and partitions.
A filesystem is “how data is written in a partition of the storage device”.
Windows, macOS/OSX and OpenWrt (Linux) use different default filesystems, and not all filesystems can be read by all equally well (if at all).
OpenWrt is a Linux-based system, so it can read and write data written in Windows and macOS filesystems, it will be slower, more limited and less reliable than when reading/writing data from native linux filesystems. So if you want to transfer data they may be good enough, but for a storage device permanently attached to your OpenWrt device, using a native Linux filesystem is recommended.
In case you wonder, the reason for this lack of performance/reliability is patents, trade secrets and other ways to impede the adoption of Windows or Apple filesystems by other parties.
To see what filesystems can be read by the firmware currently installed, write
This is an example output from a OpenWrt x86 Virtual Machine, it can read many filesystems as space is not an issue for this target. For most devices, you will have to choose what filesystems you need to be able to access, and install the package with the filesystem driver for it.
nodev sysfs nodev rootfs nodev ramfs nodev bdev nodev proc nodev tmpfs nodev binfmt_misc nodev debugfs nodev sockfs nodev bpf nodev pipefs nodev devpts ext3 ext2 ext4 squashfs nodev overlay btrfs f2fs xfs vfat
This command will download the tools needed to create and fix ext4 (and older versions)
opkg install e2fsprogs
If in the list of supported filesystems in your device you don't see ext4, you must install also the driver itself
opkg install kmod-fs-ext4
This command will download the tools needed to create and fix f2fs
opkg install f2fs-tools
If in the list of supported filesystems in your device you don't see f2fs, you must install also the driver itself
opkg install kmod-fs-f2fs
a full list of filesystems available in OpenWrt can be obtained by writing
opkg update && opkg list | grep kmod-fs
the tools for the filesystem of your choosing can be found by writing
opkg list | grep FILESYSTEM_NAME
OpenWrt has drivers and filesystem tools for ext2/3/4, f2fs, xfs and btrfs, and drivers for most other filesystems supported by Linux.
The only filesystem that is recommended for drives you will use for multiplatform usage is FAT32. It will be read by Windows, macOS/OSX, Linux, and any other device you might have (smartTV, tablets, car sound systems with usb port…). Its main drawback (for a data drive) is that it cannot store a file bigger than 3.9 GiB even if the drive itself is bigger than that. It is also prone to corruption if the device is disconnected while still writing, which can lead to data loss if the device is written again without running a filesystem check.
this command will download the tools needed to create and fix FAT32 (and older versions)
opkg install dosfstools (The dosfstools package includes the mkfs.fat and fsck.fat utilities, which respectively make and check MS-DOS FAT filesystems. Also stated above.)
If in the list of supported filesystems in your device you don't see vfat, you must install also the driver itself
opkg install kmod-fs-vfat
For some filesystems, like for FAT32, 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.
Available NLS files and their packages can be listed by writing
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 only filesystem used on Windows PC is NTFS, on OpenWrt (Linux) it is available but it's performance is low, avoid it if you can.
Another filesystem that is used on newer SD cards bigger than 32 GiB is exFAT, which is also available and has better performance and reliability than NTFS on OpenWrt. It is recommended to simply format these SD cards with FAT32, if the limitations aren't an issue for you.
This command will download the tools needed to create and fix NTFS
opkg install ntfsprogs_ntfs-3g
If in the list of supported filesystems in your device you don't see ntfs, you must install also the driver itself
opkg install ntfs-3g
See also Writable NTFS
This command will download the driver to read exfat filesystems, there are no tools available to format and check exfat in OpenWrt (as of 2017).
opkg install kmod-fs-exfat
opkg install libblkid
In Apple land you have HFS, HFS+ and APFS. Same as with Windows filesystems, there is a driver available for HFS and HFS+ but it has low performance and does not support all features.
APFS is too new (as of 2017) and there is no support at all for it in OpenWrt (nor in Linux)
This command will download the tools needed to create and fix HFS and HFS+
opkg install hfsfsck
If in the list of supported filesystems in your device you don't see hfs and hfsplus, you must install also the drivers
opkg install kmod-fs-hfs kmod-fs-hfsplus
A partition is a way to split the storage space in more different sections, each using its own independent filesystem.
This can be useful to separate different types of data, like for example to keep your expanded firmware system separated from the actual data you want to store and share, or data that must be easily accessible from Windows or MacOS directly if you disconnect the external drive.
Discussing advanced partitioning is beyond the scope of this article, as OpenWrt uses the same commandline tools used by any other Linux system.
fdisk tool is used to create/modify partitions on a drive initialized with MBR scheme
gdisk tool is used to create/modify partitions on a drive initialized with GPT scheme