Disks and File systems

File system types

HelenOS currently supports the following file systems:

File system	/srv executable	Can be initrd FS	Has mk*fs utility	Status
TMPFS	tmpfs	yes	no	Stable
FAT	fat	yes	yes	Stable
locfs	locfs	no	no	Stable
Ext2fs/Ext3fs/Ext4fs	ext4fs	yes	no	Stable
exFAT	exfat	no	yes	Testing
CDFS	cdfs	no	no	Testing
MFS	mfs	no	yes	Stable
UDF	udf	no	no	Read-only testing

HelenOS also supports the MBR/BIOS and GPT/UEFI partitioning schemes.

Directory structure

The file system of a running HelenOS system is roughly laid out as follows:

/app	end-user applications (see the Command Reference)
/cfg	system-wide configuration
/data	application data (e.g. the web root served by websrv)
/drv	device drivers
/inc	header files
/lib	libraries
/loc	location service nodes (rough analogy of /dev in UNIX)
/src	source files
/srv	server applications (services, e.g. console, networking - see the Command Reference)
/tmp	temporary files
/w	writable system volume (has free space, can be persistent)

This layout is not fixed in any way and may change in the future.

Block device drivers

Non-DDF:

file_bd	File-backed block device
rd	Initial ramdisk
sata_bd	AHCI SATA
vbd	Virtual Block Device - provides block devices for individual partitions

DDF-based:

ata_bd	ATA/ATAPI
usbmast	USB mass storage
ddisk	msim disk driver

Managing disk labels and file systems

You can use the interactive fdisk utility to create and manage disk labels. BIOS/MBR and UEFI/GPT labels are supported. When you create a partition with fdisk, you are also prompted for file system type (The file system will be initialized as part of creating the partition).

If you'd like to create a file system on a raw disk, you need to do it by manually invoking a mk*fs utility.

Here's an example fdisk session where we create a new partition table, create one partition with and Ext4 file system labeled 'Test' that will be automatically mounted at /vol/Test. Note that in several cases we just hit enter and go with the default choice.

/ # fdisk

Select device
1: devices/\hw\sys\00:01.0\ata-c1\d0 (2.097 MB)
2: devices/\hw\sys\00:01.0\ata-c2\d0 (34.09 MB)
3: Exit

Choice> 1

Device: devices/\hw\sys\00:01.0\ata-c1\d0 (2.097 MB)
Disk contains no label.
Entire disk: (No name) 2.097 MB, Empty
Select action
1: Create label
2: Exit

Choice> 1

Select label type
1: MBR [default]
2: GPT

Choice> 1

Device: devices/\hw\sys\00:01.0\ata-c1\d0 (2.097 MB)
Label type: MBR
Maximum free primary block: 2.085 MB
Total free primary space: 2.085 MB
Select action
1: Create primary partition
2: Create extended partition
3: Delete label
4: Exit

Choice> 1

Enter capacity of new partition.
?> 2.085 MB
Select file system type
1: ExFAT
2: FAT
3: MINIX
4: Ext4 [default]

Choice> 4

Enter volume label for new partition.

?> Test

Enter mount point for new partition (Auto, None or /path).
?> Auto

Device: devices/\hw\sys\00:01.0\ata-c1\d0 (2.097 MB)
Label type: MBR
Partition 1: Test 2.085 MB, Primary, Ext4
Select action
1: Modify partition
2: Delete partition
3: Delete label
4: Exit

Choice> 4

/ # vol
Volume Name Resource                            Content  Auto Mounted at     
=========== =================================== ======== ==== ===============
HelenOS-CD  devices/\hw\sys\00:01.0\ata-c2\d0p0 ISO 9660 Yes  /vol/HelenOS-CD
Test        devices/\hw\sys\00:01.0\ata-c1\d0p1 Ext4     Yes  /vol/Test      
/ # 

Accessing File Systems

In many cases the OS makes file systems available automatically. For any file system that has a volume label and is not located on the internal ATA disk drive, it should be automatically available under /vol/<volume_label>. This works for CD-ROMS and USB flash sticks, for example.

To find out which volumes are present in the system and where they are mounted, use the vol command. For example:

/ # vol
Volume Name Resource                            Content  Auto Mounted at     
=========== =================================== ======== ==== ===============
            devices/\hw\sys\00:01.0\ata-c1\d0p0 FAT                          
HelenOS-CD  devices/\hw\sys\00:01.0\ata-c2\d0p0 ISO 9660 Yes  /vol/HelenOS-CD
# 

The partition on the internal drive is not mounted by default, but we can change that using the fdisk command.

If you would like to remove a volume from the system, use the vol eject command:

# vol eject /vol/HelenOS-CD

To insert the volume back we can use either:

# vol insert -p /vol/HelenOS-CD

or

# vol insert devices/\hw\sys\00:01.0\ata-c2\d0p0

Mounting file systems manually

This should only be needed in special circumstances. In most cases use fdisk to configure the mount point. Only do this if you know what you are doing as it may break the system's idea of file system status.

Typing just mount<enter> prints out a list of mounted file systems. The basic syntax to mount a file system is:

# mount <fstype> <directory> <service-name>

fstype is the type of the file system (e.g. fat, ext4, mfs), service-name is the service name of the block device (typically of a partition; it's the long name like devices/\hw\pci...\l0p1) and directory is the directory path to mount on top of.

As service-name is long to type, try cd to /loc and then use tab-completion…

You can find the list of available partition block devices in your system by typing:

# loc show-cat partition

Unlabeled disks will be represented by one 'fake' partition spanning the entire disk.