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The df (free disk space) command will gather and summarize some important statistics about all currently mounted filesystems. The df command is easy to use, for example:
# df Filesystem 1024-blocks Used Available Capacity Mounted on /dev/hda3 497699 443871 28124 94% / /dev/hda1 509856 469632 40224 92% /mnt/dos /dev/hdc1 3868 2596 1272 67% /mnt/flash /dev/hdb 644324 644324 0 100% /mnt/cdrom
This output shows four different filesystems on three different devices mounted under Linux. The first is the root partition at the / directory on /dev/hda3; the second is a DOS partition under /mnt/dos on /dev/hda1; the third is a flashcard under /mnt/flash on /dev/hdc1; and the fourth is a CD-ROM, mounted under /mnt/cdrom on /dev/dev/hdb. The df command also lists the size of the storage device, how much has been used, how much is available, and the current capacity of the device. Notice that the CD-ROM has no space left. This is because it is mounted read-only, meaning you can't save or delete files on this device. The command shown in the next example will let you know.
One handy way to find out about the different filesystems you have mounted is to use the mount command. This command is usually used during startup, and by the root operator to mount and unmount filesystems, but you can use mount to show what type of filesystems are in use, and how the filesystems are mounted, for example:
# mount /dev/hda3 on / type ext2 (rw) /dev/hda1 on /mnt/dos type msdos (rw) none on /proc type proc (rw) /dev/hdc1 on /mnt/flash type msdos (rw) /dev/hdb on /mnt/cdrom type iso9660 (ro)
This shows that your root partition, on the / directory, is a Linux ext2 filesystem mounted read-write, whereas /mnt/dos and /mnt/flash contain DOS partitions, also read-write. (The /proc filesystem is a special directory Linux uses for process reporting, such as running applications, system state, and so on.) Finally, mount reports that your CD-ROM is mounted as a read-only iso9660 filesystem.
You can use this information from mount to get specific information with the df command, by using the df command's -t, or filesystem, option, as follows:
# df -t ext2 Filesystem 1024-blocks Used Available Capacity Mounted on /dev/hda3 497699 443873 28122 94% /
This tells df to just show information about any mounted Linux filesystems. You can get a list of valid filesystems to specify with the df command by looking at the mount manual page. The mount command is covered in more detail in Hour 21, "Handling Files." You can see
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that by using the df and mount command, you can get reports on the type of mounted devices, how the devices are mounted, and how much room you have left on each.
The du (disk usage) command conveniently summarizes how your disk is being used, by reporting the amount of space required by each directory or specified path. Although the du command has more than 20 command-line options, this section presents some of the common ones, and leaves it up to you to experiment. You can use the du command by itself, or specify a directory or path, for example:
# du 904 ./book 12080 ./mail 1 ./.tin/.mailidx 1 ./.tin/.index 10 ./.tin ... 589 ./News 9 ./.index 7 ./.procmail 5 ./.ncftp 418 ./reading 778 ./documents 27199 .
This report (for brevity, not all the directories are listed) shows the contents of a home directory, with a total for 27,199 1-kilobyte blocks. If you find this hard to understand, you can have du report the size in bytes, for example:
# du -b 897606 ./book 12294410 ./mail 1024 ./.tin/.mailidx 1024 ./.tin/.index 9382 ./.tin 561715 ./News 4033 ./.index 4139 ./.procmail 2791 ./.ncftp 424037 ./reading 784216 ./documents 26785752 .
If this is too much information for you, then you can use the --summarize option to get the total in either kilobytes or bytes, as follows:
# du -b --summarize 26786903 .
The du command can also help you keep track of directories which, unattended, sometimes grow out of control or use a lot of disk space. If you specify a path, du will report on the
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different size of the directories, pinpointing any that may contain too much information, for example:
# du --summarize -b /var/* | sort -nr 6474535 /var/lib 2336494 /var/log 868163 /var/catman 76362 /var/spool 14591 /var/dt 2385 /var/run 2048 /var/lock 2048 /var/local 1024 /var/tmp 1024 /var/preserve 1024 /var/nis
Here I've combined the du command, which has been instructed to summarize the number of bytes in each directory, with the sort command, which has been set to use a numerical sort in reverse order. This one-liner, which uses pipes (discussed in Hour 6, "Using the Shell"), will automatically print the largest directories at the top of the output list. You can see that the /var/log directory is getting pretty big. The /var/lib directory will be large because it contains the rpm databases (rpm is discussed in Hour 22, "Red Hat Tools").
Although the du command does not, like the df command, have a -t option to specify which filesystem to report on, you can use the -x option to exclude other filesystems. Or, you can have du report on other filesystems by specifying a usage report at the mount point. For example, du will merrily chug along and summarize how much room your Windows directories take up:
# du -b --summarize /mnt/dos/* | sort -nr 129486405 /mnt/dos/windows 23929345 /mnt/dos/msoffice 20811654 /mnt/dos/photoenf 7744046 /mnt/dos/tranxit 6828902 /mnt/dos/org2 6647520 /mnt/dos/laplink 5556496 /mnt/dos/acrobat3 4041127 /mnt/dos/pcdr 3753962 /mnt/dos/psp 3603469 /mnt/dos/insync 3176769 /mnt/dos/antvirus 2669335 /mnt/dos/airlite 2408920 /mnt/dos/winfax ...
This (shortened) report shows that next to the operating system, the largest space is taken up by certain applications. This information can be helpful in making a decision on what applications to uninstall if you need more disk space.