| // 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. | |
| package mountinfo |