Linux Command Line - Disk Usage and Disk Filesystem
du displays disk usage information and
df displays disk filesystem information. These commands also work on Mac OS X.
du <path> displays size of each subdirectory in the path and the total sum of the size of all directories in the path in bytes.
du is equivalent to
du -h displays the data in human readable format. It round sizes up to their largest unit and the unit abbreviation: bytes
du -sh provides the total size of the path in human readable format. It may be slow if there are many subdirectories.
- 1 bit
- 1 byte
B= 8 bits
- 1 kilobyte
KB(1024) = 1024 bytes
- 1 megabyte
MB(1024^2) = 1024 kilobytes
- 1 gigabyte
GB(1024^3) = 1024 gigabytes
- 1 terabyte
TB(1024^4) = 1024 gigbaytes
df displays device name, block size, disk space, used disk space, available disk space and mount points.
df -h displays the same as above but in human readable format.
A sequence of bytes or bits of a particular length, the block size. Putting data into blocks is blocking and extracting data from a block is deblocking. It helps reduce overhead and speed up data streams.
mount command instructs an operating system that a file system is ready for use. It associates a point in the file system (the mount point) to another file system. File systems, files, directories and devices (USB, CD-ROMs, DVDs, etc.) can be mounted.
umount dissociates a mount point from its filesystem.
A device file is an interface for a device driver that appears in the file system as if it were an ordinary file. In Unix systems most devices appear as files in a virtual file system.
A Unix data structure that describe objects in a file system like files and directories. It stores disk block location, owner and permissions data and time of last change, access and modification.
POSIX standards requires the following:
- size of file in bytes
- device id of the device the file belongs to
- file owner’s user id
- file’s group id
- file mode
- system and user flags
- inode last modified, file content last modified and time last accessed
- count of hard links pointing to the inode
- pointers to the disk blocks that store the file’s contents