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File: coreutils.info, Node: df invocation, Next: du invocation, Up: Disk usage
14.1 'df': Report file system disk space usage
==============================================
'df' reports the amount of disk space used and available on file
systems. Synopsis:
df [OPTION]... [FILE]...
With no arguments, 'df' reports the space used and available on all
currently mounted file systems (of all types). Otherwise, 'df' reports
on the file system containing each argument FILE.
Normally the disk space is printed in units of 1024 bytes, but this
can be overridden (*note Block size::). Non-integer quantities are
rounded up to the next higher unit.
For bind mounts and without arguments, 'df' only outputs the
statistics for that device with the shortest mount point name in the
list of file systems (MTAB), i.e., it hides duplicate entries, unless
the '-a' option is specified.
With the same logic, 'df' elides a mount entry of a dummy pseudo
device if there is another mount entry of a real block device for that
mount point with the same device number, e.g. the early-boot pseudo
file system 'rootfs' is not shown per default when already the real root
device has been mounted.
If an argument FILE resolves to a special file containing a mounted
file system, 'df' shows the space available on that file system rather
than on the file system containing the device node. GNU 'df' does not
attempt to determine the disk usage on unmounted file systems, because
on most kinds of systems doing so requires extremely nonportable
intimate knowledge of file system structures.
The program accepts the following options. Also see *note Common
options::.
'-a'
'--all'
Include in the listing dummy, duplicate, or inaccessible file
systems, which are omitted by default. Dummy file systems are
typically special purpose pseudo file systems such as '/proc', with
no associated storage. Duplicate file systems are local or remote
file systems that are mounted at separate locations in the local
file hierarchy, or bind mounted locations. Inaccessible file
systems are those which are mounted but subsequently over-mounted
by another file system at that point, or otherwise inaccessible due
to permissions of the mount point etc.
'-B SIZE'
'--block-size=SIZE'
Scale sizes by SIZE before printing them (*note Block size::). For
example, '-BG' prints sizes in units of 1,073,741,824 bytes.
'--direct'
Do not resolve mount point and show statistics directly for a file.
It can be especially useful for NFS mount points if there is a
boundary between two storage policies behind the mount point.
'--total'
Print a grand total of all arguments after all arguments have been
processed. This can be used to find out the total disk size, usage
and available space of all listed devices.
For the grand total line, 'df' prints '"total"' into the SOURCE
column, and '"-"' into the TARGET column. If there is no SOURCE
column (see '--output'), then 'df' prints '"total"' into the TARGET
column, if present.
'-h'
'--human-readable'
Append a size letter to each size, such as 'M' for mebibytes.
Powers of 1024 are used, not 1000; 'M' stands for 1,048,576 bytes.
This option is equivalent to '--block-size=human-readable'. Use
the '--si' option if you prefer powers of 1000.
'-H'
Equivalent to '--si'.
'-i'
'--inodes'
List inode usage information instead of block usage. An inode
(short for index node) contains information about a file such as
its owner, permissions, timestamps, and location on the disk.
'-k'
Print sizes in 1024-byte blocks, overriding the default block size
(*note Block size::). This option is equivalent to
'--block-size=1K'.
'-l'
'--local'
Limit the listing to local file systems. By default, remote file
systems are also listed.
'--no-sync'
Do not invoke the 'sync' system call before getting any usage data.
This may make 'df' run significantly faster on systems with many
disks, but on some systems (notably SunOS) the results may be
slightly out of date. This is the default.
'--output'
''--output'[=FIELD_LIST]'
Use the output format defined by FIELD_LIST, or print all fields if
FIELD_LIST is omitted. In the latter case, the order of the
columns conforms to the order of the field descriptions below.
The use of the '--output' together with each of the options '-i',
'-P', and '-T' is mutually exclusive.
FIELD_LIST is a comma-separated list of columns to be included in
'df''s output and therefore effectively controls the order of
output columns. Each field can thus be used at the place of
choice, but yet must only be used once.
Valid field names in the FIELD_LIST are:
'source'
The source of the mount point, usually a device.
'fstype'
File system type.
'itotal'
Total number of inodes.
'iused'
Number of used inodes.
'iavail'
Number of available inodes.
'ipcent'
Percentage of IUSED divided by ITOTAL.
'size'
Total number of blocks.
'used'
Number of used blocks.
'avail'
Number of available blocks.
'pcent'
Percentage of USED divided by SIZE.
'file'
The file name if specified on the command line.
'target'
The mount point.
The fields for block and inodes statistics are affected by the
scaling options like '-h' as usual.
The definition of the FIELD_LIST can even be splitted among several
'--output' uses.
#!/bin/sh
# Print the TARGET (i.e., the mount point) along with their percentage
# statistic regarding the blocks and the inodes.
df --out=target --output=pcent,ipcent
# Print all available fields.
df --o
'-P'
'--portability'
Use the POSIX output format. This is like the default format
except for the following:
1. The information about each file system is always printed on
exactly one line; a mount device is never put on a line by
itself. This means that if the mount device name is more than
20 characters long (e.g., for some network mounts), the
columns are misaligned.
2. The labels in the header output line are changed to conform to
POSIX.
3. The default block size and output format are unaffected by the
'DF_BLOCK_SIZE', 'BLOCK_SIZE' and 'BLOCKSIZE' environment
variables. However, the default block size is still affected
by 'POSIXLY_CORRECT': it is 512 if 'POSIXLY_CORRECT' is set,
1024 otherwise. *Note Block size::.
'--si'
Append an SI-style abbreviation to each size, such as 'M' for
megabytes. Powers of 1000 are used, not 1024; 'M' stands for
1,000,000 bytes. This option is equivalent to '--block-size=si'.
Use the '-h' or '--human-readable' option if you prefer powers of
1024.
'--sync'
Invoke the 'sync' system call before getting any usage data. On
some systems (notably SunOS), doing this yields more up to date
results, but in general this option makes 'df' much slower,
especially when there are many or very busy file systems.
'-t FSTYPE'
'--type=FSTYPE'
Limit the listing to file systems of type FSTYPE. Multiple file
system types can be specified by giving multiple '-t' options. By
default, nothing is omitted.
'-T'
'--print-type'
Print each file system's type. The types printed here are the same
ones you can include or exclude with '-t' and '-x'. The particular
types printed are whatever is supported by the system. Here are
some of the common names (this list is certainly not exhaustive):
'nfs'
An NFS file system, i.e., one mounted over a network from
another machine. This is the one type name which seems to be
used uniformly by all systems.
'ext2, ext3, ext4, xfs, btrfs...'
A file system on a locally-mounted hard disk. (The system
might even support more than one type here; Linux does.)
'iso9660, cdfs'
A file system on a CD or DVD drive. HP-UX uses 'cdfs', most
other systems use 'iso9660'.
'ntfs,fat'
File systems used by MS-Windows / MS-DOS.
'-x FSTYPE'
'--exclude-type=FSTYPE'
Limit the listing to file systems not of type FSTYPE. Multiple
file system types can be eliminated by giving multiple '-x'
options. By default, no file system types are omitted.
'-v'
Ignored; for compatibility with System V versions of 'df'.
An exit status of zero indicates success, and a nonzero value
indicates failure. Failure includes the case where no output is
generated, so you can inspect the exit status of a command like 'df -t
ext3 -t reiserfs DIR' to test whether DIR is on a file system of type
'ext3' or 'reiserfs'.
Since the list of file systems (MTAB) is needed to determine the file
system type, failure includes the cases when that list cannot be read
and one or more of the options '-a', '-l', '-t' or '-x' is used together
with a file name argument.
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