github.com/moby/sys/mountinfo

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 OpenBSD, 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 efficient 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, and being cleaned (i.e. no extra slashes or dots). 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 over-mounts), 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.