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Diffstat (limited to 'vendor/github.com/moby/sys/mountinfo/doc.go')
| -rw-r--r-- | vendor/github.com/moby/sys/mountinfo/doc.go | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/vendor/github.com/moby/sys/mountinfo/doc.go b/vendor/github.com/moby/sys/mountinfo/doc.go new file mode 100644 index 000000000..21aa8dd59 --- /dev/null +++ b/vendor/github.com/moby/sys/mountinfo/doc.go @@ -0,0 +1,47 @@ +// Package mountinfo provides a set of functions to retrieve information about OS mounts. +// Currently it supports Linux. For historical reasons, there is also some support for FreeBSD, +// and a shallow implementation for Windows, but in general this is Linux-only package, so +// the rest of the document only applies to Linux, unless explicitly specified otherwise. +// +// In Linux, information about mounts seen by the current process is available from +// /proc/self/mountinfo. Note that due to mount namespaces, different processes can +// see different mounts. A per-process mountinfo table is available from /proc/<PID>/mountinfo, +// where <PID> is a numerical process identifier. +// +// In general, /proc is not a very effective interface, and mountinfo is not an exception. +// For example, there is no way to get information about a specific mount point (i.e. it +// is all-or-nothing). This package tries to hide the /proc ineffectiveness by using +// parse filters while reading mountinfo. A filter can skip some entries, or stop +// processing the rest of the file once the needed information is found. +// +// For mountinfo filters that accept path as an argument, the path must be: +// - absolute; +// - having all symlinks resolved; +// - being cleaned. +// +// One way to achieve all of the above is to employ filepath.Abs followed by +// filepath.EvalSymlinks (the latter calls filepath.Clean on the result so +// there is no need to explicitly call filepath.Clean). +// +// NOTE that in many cases there is no need to consult mountinfo at all. Here are some +// of the cases where mountinfo should not be parsed: +// +// 1. Before performing a mount. Usually, this is not needed, but if required (say to +// prevent overmounts), to check whether a directory is mounted, call os.Lstat +// on it and its parent directory, and compare their st.Sys().(*syscall.Stat_t).Dev +// fields -- if they differ, then the directory is the mount point. NOTE this does +// not work for bind mounts. Optionally, the filesystem type can also be checked +// by calling unix.Statfs and checking the Type field (i.e. filesystem type). +// +// 2. After performing a mount. If there is no error returned, the mount succeeded; +// checking the mount table for a new mount is redundant and expensive. +// +// 3. Before performing an unmount. It is more efficient to do an unmount and ignore +// a specific error (EINVAL) which tells the directory is not mounted. +// +// 4. After performing an unmount. If there is no error returned, the unmount succeeded. +// +// 5. To find the mount point root of a specific directory. You can perform os.Stat() +// on the directory and traverse up until the Dev field of a parent directory differs. + +package mountinfo |