= 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''' ||
|| [wiki:Fs/Tmpfs TMPFS]   || `tmpfs`         || yes            || no                  || Stable ||
|| [wiki:Fs/Fat FAT]       || `fat`           || yes            || yes                 || Stable ||
|| [wiki:Fs/Locfs locfs]   || `locfs`         || no             || no                  || Stable ||
|| [wiki:Fs/Ext2fs Ext2fs/Ext3fs/Ext4fs] || `ext4fs`        || yes            || no                 || Stable ||
|| [wiki:Fs/ExFat exFAT]   || `exfat`         || no             || yes                 || Testing ||
|| [wiki:Fs/Cdfs CDFS]     || `cdfs`          || no             || no                  || Testing ||
|| [wiki:Fs/Mfs MFS]       || `mfs`           || no             || yes                 || Stable ||
|| [wiki:Fs/UDF UDF]       || `udf`           || no             || no                  || Read-only testing ||

== Directory structure ==

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

|| /app  || end-user applications (see the [wiki:CommandReference 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 [wiki:CommandReference Command Reference]) ||
|| /tmp  || temporary files ||

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 ||
|| part || Disk label/partition driver - provides block devices for individual partitions ||
|| rd || Initial ramdisk ||
|| sata_bf || AHCI SATA ||

DDF-based:

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

== Working with 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.

== Mounting file systems ==

In order to make use of a file system it needs to be mounted into the filesystem namespace
using the {{{mount}}} command. Typing just {{{mount<enter>}}} prints out a list of mounted
file systems. Te basic syntax to mount a file system is:

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

{{{fstype}}} is the type of the file system (e.g. {{{ext4}}}, {{{mfs}}}), {{{service-name}}} is
the service name of the block device (typically of a partition) and {{{directory}}} is the directory path
to mount on top of.

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.