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Disk

Print partitions, space usage, file system, etc

Module type	disk
Default order	42 (only used by --gen-config)
Module source	src/modules/disk/disk.c
Detection source	src/detection/disk/

Prints one line per mounted volume: used and total size, the percentage in use, the file system and any volume-type labels. The key is Disk (<mount point>), so every volume is labelled with the mount point it belongs to — a custom key is shared by all of them, and {index} is the only way to tell the lines apart.

Disk (/): 45.30 GiB / 100.00 GiB (45%) - ext4
Disk (/boot): 300.00 MiB / 1024.00 MiB (29%) - vfat [External]
Disk (/srv/data): Unknown - zfs [Subvolume]

The sizes go through display.size (so binaryPrefix: si prints 48.64 GB), the percentage is styled by this module's percent thresholds, and the bracket at the end lists the volume-type flags that are set — External, Subvolume, Hidden, Read-only, in that order and comma separated. A volume whose total size cannot be read prints the literal word Unknown instead of used / total (and gets the Unknown type in the JSON result, which has no label of its own in the text output).

Platform support

Platform	Implementation	Notes
Linux	disk_linux.c	/proc/mounts plus statvfs(); birth time via statx()
Android	disk_linux.c	Same file, with the /dev checks compiled out
GNU/Hurd	disk_linux.c	Same file
FreeBSD	disk_bsd.c	getfsstat(); volume labels need libgeom at build time
NetBSD	disk_bsd.c	Same file, switched to getvfsstat()
OpenBSD	disk_bsd.c	Same file; birth time comes from __st_birthtim
Solaris / illumos	disk_sunos.c	/etc/mnttab; the volume name is the fstr of the mount
Haiku	disk_haiku.cpp	next_dev() / fs_stat_dev()
macOS	disk_bsd.c	getfsstat(); volume name via getattrlist()
Windows	disk_windows.c	NtQueryInformationProcess(ProcessDeviceMap) and NtQueryVolumeInformationFile

All ten platforms have a real implementation, so the module never reports "Not supported on this platform". There is no disk_nosupport.c in the tree.

Configuration

Key	Type	Default	Description
folders	string or array	empty — every mount point	Restrict the output to these mount points. Overrides every show* option.
hideFolders	string or array	/efi:/boot:/boot/* on Linux, the BSDs, Solaris and Haiku; empty on macOS, Windows and Android	Mount points or fnmatch glob patterns to hide
hideFS	string or array	empty	File system names to hide (apfs, ext4, tmpfs, drvfs, …)
showRegular	boolean	true	Show regular volumes
showExternal	boolean	true	Show external / removable / network volumes
showHidden	boolean	false	Show hidden volumes
showSubvolumes	boolean	false	Show subvolumes (btrfs subvolumes, ZFS datasets)
showReadOnly	boolean	true	Show read-only volumes
showUnknown	boolean	false	Show volumes whose sizes cannot be detected
useAvailable	boolean	false	Compute used bytes from f_bavail (Windows: CallerAvailableAllocationUnits) instead of f_bfree
percent	object	{ "green": 50, "yellow": 80, "type": 0 }	Colour thresholds and style for the percentage. type: 0 inherits display.percentType.
key	string	Disk (<mount point>)	Module key. A single space hides the key and the separator.
keyColor	color	–	Overrides display.color.keys
keyIcon	string	built-in glyph	Printed when display.key.type includes the icon bit. Any glyph works; "" prints none.
keyWidth	integer	–	Overrides display.key.width
outputColor	color	–	Overrides display.color.output
format	string	–	Custom output format (see below)
condition	object	–	Show the module only if the conditions match

folders, hideFolders and hideFS accept either a separated string or an array of strings. The separator is : on POSIX and ; on Windows. Entries in hideFolders are fnmatch patterns, so /run/* hides every mount point below /run.

The default showTypes mask is showRegular | showExternal | showReadOnly — the module is built around the assumption that the volumes you want to see are the regular, local, mounted ones, whether or not they happen to be read-only. macOS makes that concrete: the sealed system volume at / is read-only, and hiding read-only volumes by default would hide the root file system.

Format string

Run fastfetch -h disk-format for the authoritative list.

Variable	Description
{size-used}	Used size, formatted with display.size
{size-total}	Total size, formatted
{size-free}	Free size (f_bfree), formatted
{size-available}	Size available to an unprivileged user (f_bavail), formatted
{size-percentage}	Used percentage as a number; empty unless the percentage style includes the number
{size-percentage-bar}	Used percentage as a bar, brackets included; empty unless the percentage style includes a bar
{files-used}	Inodes used
{files-total}	Inodes total
{files-percentage}	Inode usage as a number; empty unless the number style is enabled
{files-percentage-bar}	Inode usage as a bar; empty unless the bar style is enabled
{filesystem}	File system name — also available in key format
{name}	Volume label / name — also available in key format
{mountpoint}	Mount point — also available in key format
{mount-from}	Source of the mount (device path, or zroot/ROOT/default on ZFS) — also available in key format
{is-external}	true if the volume is external
{is-hidden}	true if the volume is hidden
{is-readonly}	true if the volume is read-only
{create-time}	Creation time in local time, YYYY-MM-DD hh:mm:ss; empty when unknown
{years}, {days-of-year}, {years-fraction}	Age of the volume as whole years, the day within the current year, and a fractional year (0.05)
{days}, {hours}, {minutes}, {seconds}, {milliseconds}	Age broken down into days, hours, minutes, seconds and milliseconds

Variables available only in key format

The key format string is parsed separately, so it has three names that the output format does not have:

Variable	Description
{index}	1-based counter over the volumes that are actually printed
{mountpoint-link}	The mount point wrapped in an OSC 8 hyperlink pointing at file://<mount point>
{name-link}	The volume name wrapped in the same hyperlink

Inside WSL with Windows Terminal (WSL_DISTRO_NAME and WT_SESSION both set) the links are rewritten to file:///<drive>:/ for 9p mounts and to file:////wsl.localhost/<distro><path> otherwise, so clicking the key opens the volume in Explorer. Everywhere else the link target is just file://<mount point>, which most terminals treat as a local path.

JSON output

{
    "type": "Disk",
    "result": [
        {
            "bytes": { "available": 160183455744, "free": 160183455744, "total": 900000120832, "used": 739816665088 },
            "files": { "total": 1564775574, "used": 484014 },
            "filesystem": "apfs",
            "mountpoint": "/",
            "mountFrom": "/dev/disk1s1s1",
            "name": "System",
            "volumeType": ["Regular", "Read-only"],
            "createTime": "2024-03-01T12:00:00.000+0800"
        }
    ]
}

All byte values are raw numbers, volumeType is an array of strings in the order Regular, External, Subvolume, Hidden, Read-only, Unknown, and createTime is either the full ISO-8601 stamp or null. files.total and files.used are both null when the file system does not report inode counts at all (the Windows file system in WSL returns 0/0, which is turned into null). On a detection failure the object is { "type": "Disk", "error": "…" }.

Examples

{ "type": "disk", "folders": "/", "format": "{size-used} / {size-total} ({size-percentage})" }

// Show only the root file system, with a bar
{
    "type": "disk",
    "folders": "/",
    "percent": { "type": ["num", "bar"] },
    "format": "{size-percentage-bar} {size-used} / {size-total}"
}

// Hide everything on a network file system, and the ESP
{ "type": "disk", "hideFS": "nfs:nfs4:cifs", "hideFolders": "/efi:/boot/*" }

// Make every line clickable, and show the volume label as the key
{ "type": "disk", "key": "{mountpoint-link}", "format": "{name} {size-used} / {size-total}" }

Pitfalls

• folders matches mount points, not directories. The entries are compared against the mount point string for equality, so "/home/user" finds nothing when /home is the mount point, and "/" finds the root file system. The presets follow this rule ("/", "/:/home:/boot:/efi", and on macOS "/System/Volumes/VM" to reach a volume that is hidden by default).
• folders silently disables every show* option. The filter only runs when folders is empty, which is what the schema means by "This option overrides other show* options": with "folders": "/" you get / even if you also wrote "showRegular": false.
• show* filters are applied to the text output only. --format json calls the same detector but never applies the mask, so "showRegular": false prints nothing on screen while the JSON result still lists every regular volume. folders, hideFolders and hideFS are honoured by both, because they are applied during detection.
• The filters run after the key is built and are completely silent. A configuration that hides everything prints no line and no error — the module still reports success. Do not read "no output" as "not supported".
• The default showReadOnly is true, not false. doc/json_schema.json claims false; the initialiser adds the read-only bit to the default mask, and read-only volumes appear in the default output.
• hideFolders has a platform-dependent default. On Linux, the BSDs, Solaris, Haiku and GNU/Hurd it is /efi:/boot:/boot/*, which hides the ESP and the boot partition — so a machine with a separate /boot prints one line where lsblk shows two. On macOS, Windows and Android it is empty. An explicit hideFolders replaces the default, so hiding one extra directory means listing the boot patterns again.
• A run with --format json and no folders includes volumes the text output never shows — every hidden APFS helper volume, every Unknown volume, and (on Windows) every letter that maps to a drive with no media.
• {size-percentage} and {size-percentage-bar} can be empty. Both are computed only when the active percentage style asks for them: the number needs the num flag and the bar needs a bar flag. The display default is ["num", "num-color"], so the number works and the bar renders as an empty string until percent.type (or display.percentType) adds "bar". {size-percentage-bar} brings its own [ ], so [{size-percentage-bar}] prints [[ ■■■■■■■■-- ]].
• On macOS, / and its data volume report the same total and free figures. APFS shares one free-space pool between the volumes of a container, and f_bfree is a property of the container, so Disk (/) and Disk (/System/Volumes/Data) contain the same numbers (only used differs, by whatever was written between the two statvfs() calls). The data volume is typed Hidden, so the default configuration prints / only. useAvailable exists for the same reason: on macOS f_bfree counts the APFS reserved blocks, and the schema suggests it "may be required for macOS to display correct results" when the numbers disagree with Finder.
• f_bfree and f_bavail differ, and the module prints both. {size-free} is everything the file system considers free; {size-available} is what an unprivileged process may still write. They differ whenever the file system holds something back — ext4's reserved blocks, a ZFS reservation — and used is total − free unless useAvailable is set. On a file system with nothing reserved (a container's plain ext4, for instance) the two differ only by the few blocks written between the two readings.
• The Read-only label on macOS does not mean a read-only disk. It comes from MNT_RDONLY, which macOS sets for the sealed system snapshot at / on every modern install.
• Unknown is a size, not an error. When statvfs() fails (a share whose server went away, a drive with no media), the volume keeps bytesTotal == 0, gets the Unknown type bit and prints Unknown in place of the sizes. It is hidden by default (showUnknown: false) but still appears in the JSON result.
• Unknown in volumeType has no counterpart in the text output. The bracket only knows External, Subvolume, Hidden and Read-only; the Unknown bit shows up in the JSON array and as the missing sizes. A parser that maps volumeType to the bracket list will not round-trip.

Implementation

Every platform implements only ffDetectDisksImpl(); the shared disk.c then sorts the list alphabetically by mount point — which is also the order the volumes are printed in — marks volumes with bytesTotal == 0 as Unknown and fills in bytesUsed as bytesTotal − (free | available) according to useAvailable. The per-volume printing, the key, the show* mask and the JSON writer all live in the module.

There is no cache in this module: ffPrintDisk() and ffGenerateDiskJsonResult() each call the detector, so under --dynamic-interval the volumes are re-read on every round. The one piece of state that survives a call is FreeBSD's geom_gettree() result, which is deliberately reused because the geom tree is expensive to build.

Linux, Android and GNU/Hurd

/proc/mounts is read with setmntent()/getmntent(). Each entry is tested by isPhysicalDevice() unless folders was given: the root mount is always kept, none sources, pseudo file systems without a /dev/ source, loop*, ram* and fd* devices and Bedrock Linux's /bedrock/* mounts are dropped, and everything else must stat as a block device. 9p mounts are kept only when their options contain aname=drvfs — that is the WSL interop mount — while zfs, bcachefs and fuse.sshfs are always kept. On Android the /dev checks are skipped (the directory is not readable there) and /apex/* is dropped instead.

The volume name is looked up by stat()ing the device and scanning /dev/disk/by-label/ and then /dev/disk/by-partlabel/ for a directory entry with the same inode number; the name is then run through ffStrbufDecodeHexEscapeSequences() to turn \x20 escapes into spaces. The type is Hidden for x-gvfs-hide/hidden mount options, Subvolume when a device already appeared earlier in the sorted list (btrfs subvolumes, ZFS datasets), External when /sys/class/block/<dev>/removable is 1, and Regular otherwise; ro adds the Read-only bit. Sizes come from statvfs(), and the creation time from a statx() STATX_BTIME call, rejected when it is before 1991 (the field is not always real).

FreeBSD, NetBSD, OpenBSD and macOS

getfsstat() (NetBSD: getvfsstat()) returns the mount table. Without folders, only /, /dev/ sources, zfs and fusefs.sshfs are kept. FreeBSD reads volume labels out of the geom tree (geom_gettree(), class LABEL) and needs libgeom available at build time — otherwise the label is silently left empty. NetBSD's statvfs has signed counters and its f_flags/f_frsize are aliased to the statfs names.

On macOS the name comes from getattrlist(ATTR_CMN_NAME) on the mount point, and the type is Hidden for MNT_DONTBROWSE, External for MNT_REMOVABLE or a non-local mount, Regular otherwise. The creation time is st_birthtimespec, which DragonFly BSD does not have.

Solaris and illumos

/etc/mnttab is parsed with getmntent(). Without folders, only /, zfs and block devices under /dev/ are kept. staymntopt(MNTOPT_NOBROWSE) makes a volume Hidden, MNTOPT_RO adds Read-only; there is no External detection on this platform. The volume name is the fstr field of the statvfs result, trimmed.

Haiku

next_dev() walks the device list, fs_stat_dev() fills in the block and node counters and BDirectory/BPath turn the root node into a mount-point path. B_FS_IS_PERSISTENT unset means Hidden, B_FS_IS_READONLY means Read-only, B_FS_IS_REMOVABLE means External, and a volume with none of them is Regular. The creation time comes from BDirectory::GetCreationTime().

Windows

NtQueryInformationProcess(ProcessDeviceMap) returns the drive map and the type of each letter; DRIVE_NO_ROOT_DIR is skipped unless folders asked for it. Each drive is opened with FILE_FLAG_BACKUP_SEMANTICS and queried three times: FileFsAttributeInformation gives the file system name and the read-only flag, FileFsVolumeInformation gives the label and the creation time, and FileFsFullSizeInformation gives total, free and caller-available sizes from the allocation unit counts. mountFrom is the DOS device path from QueryDosDeviceW(). A folders value of "/" is rewritten to <system drive>:\ before matching, which is what makes the cross-platform presets work.