2.12 Filesystems

A filesystem is a section of a disk, either on the local host or mounted from a remote host over a network. Searching network filesystems can be slow, so it is common to make find avoid them.

There are two ways to avoid searching certain filesystems. One way is to tell find to only search within the same filesystem as the start-point currently being searched:

Option: -mount

Ignore files on other devices. Do not visit or search inside mount points. Do not search inside directories within other file systems even if they are the target of a symbolic link and find is following symbolic links (e.g. due to the ‘-L’ or ‘-H’ option).

Option: -xdev

Visit mount points but not their children (that is, don’t descend into directories on other devices). Using -mount -xdev has the same effect as ‘-mount’.

Here we see that normally, find will search inside a file system which is mounted at ‘tree/bound1’:

$ find tree -printf 'device: %5D path: %p\n'
device:    40 path: tree
device: 64770 path: tree/bound1
device: 64770 path: tree/bound1/on-another-fs

If we specify ‘-xdev’ then we will visit the mount point but not search inside it:

$ find tree -xdev -printf 'device: %5D path: %p\n'
device:    40 path: tree
device: 64770 path: tree/bound1

If we specify ‘-mount’ we will not visit the mount point at all:

$ find tree -mount -printf 'device: %5D path: %p\n'
device:    40 path: tree

We used the ‘%D’ directive of ‘-printf’ in those examples to shows the device number for each item, to illustrate that the files are on different devices. See Print File Information.

The other way to avoid particular filesystems is to check the type of filesystem each file is on, and not descend directories that are on undesirable filesystem types:

Test: -fstype type

True if the file is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is:

autofs ext3 ext4 fuse.sshfs nfs proc sshfs sysfs ufs tmpfs xfs

You can use ‘-printf’ with the ‘%F’ directive to see the types of your filesystems. ‘-fstype’ is usually used with ‘-prune’ to avoid searching remote filesystems (see Directories).