FS_SNAPSHOT_CREATE(2)       BSD System Calls Manual      FS_SNAPSHOT_CREATE(2)

NAME
     fs_snasphot_create -- create read only snapshot of a mounted filesystem

SYNOPSIS
     #include <sys/attr.h>
     #include <sys/snapshot.h>

     int
     fs_snapshot_create(int dirfd, const char * name, uint32_t flags);

     int
     fs_snapshot_delete(int dirfd, const char * name, uint32_t flags);

     int
     fs_snapshot_list(int dirfd, struct attrlist * name, void * attrbuf,
         size_t bufsize, uint32_t flags);

     int
     fs_snapshot_rename(int dirfd, const char * old, const char * new,
         uint32_t flags);

     int
     fs_snapshot_mount(int dirfd, const char * dir, const char * snapshot,
         uint32_t flags);

     int
     fs_snapshot_revert(int dirfd, const char * name, uint32_t flags);

DESCRIPTION
     The fs_snapshot_create() function, for supported Filesystems, causes a
     snapshot  of the Filesystem to be created. A snapshot is a read only copy
     of the filesystem frozen at a point in time.  The Filesystem is identi-
     fied by the dirfd parameter which should be a file descriptor associated
     with the root directory of the filesystem for which the snapshot is to be
     created.  name can be any valid name for a component name (except . and
     ..).  The fs_snapshot_delete() function causes the named snapshot name to
     be deleted and the fs_snapshot_rename() function causes the named snap-
     shot old to be renamed to the name new.  Available snapshots along with
     their attributes can be listed by calling fs_snapshot_list() which is to
     be used in exactly the same way as getattrlistbulk(2).  The flags parame-
     ter specifies the options that can be passed. No options are currently
     defined.

     Snapshots may be useful for backing up the Filesystem and to restore the
     Filesystem to a previous state.  Snapshots are expected to consume no
     additional storage on creation but  might consume additional storage as
     the active Filesystem is modified. Similarly deletion of files on the
     active filesystem may not result in the storage being available if the
     snapshot contains the file. Additionally, the underlying Filesystem may
     impose a limit on the number of snapshots that can be taken. For support-
     ing Filesystems, a snapshot may be used as a source for a mount. This can
     be done by the fs_snapshot_mount() function. The snapshot will be mounted
     read only. When a snapshot is mounted, it cannot be deleted but it can be
     renamed.  To revert the filesystem to a previous snapshot, the
     fs_snapshot_revert() can be used. It should be noted that reverting a
     filesystem to a snapshot is a destructive operation and causes all
     changes made to the filesystem (including snapshots created after the
     snapshot being reverted to) to be lost.

     All snapshot functions  require superuser privileges and also require an
     additional entitlement.

RETURN VALUES
     Upon successful completion, fs_snapshot_create() , fs_snapshot_delete()
     and fs_snapshot_rename() returns 0. Otherwise, a value of -1 is returned
     and errno is set to indicate the error.  fs_snapshot_list() returns the
     number of entries successfully read. A return value of 0 indicates there
     are no more entries.  Otherwise, a value of -1 is returned and errno is
     set to indicate the error. Return values are the same as
     getattrlistbulk(2).

COMPATIBILITY
     Not all volumes support snapshots. A volume can be tested for snapshot
     support by using getattrlist(2) to get the volume capabilities attribute
     ATTR_VOL_CAPABILITIES, and then testing the VOL_CAP_INT_SNAPSHOT flag.

ERRORS
     The fs_snapshot_create() , fs_snapshot_delete() , fs_snapshot_rename()
     and fs_snapshot_list() function will fail if:

     [EACCES]           Read permissions are denied for the caller on the
                        filesystem

     [ENOTSUP]          The underlying filesystem does not support this call.

     [EINVAL]           The value of the flags parameter is invalid.

     [ENOSPC]           There is no free space remaining on the file system
                        containing the file.

     [ENOSPC]           The limit for the maximum number of snapshots for a
                        filesystem has been reached.

     [EIO]              An I/O error occurred while reading from or writing to
                        the file system.

     [EPERM]            The calling process does not have appropriate privi-
                        leges.

     [EROFS]            The requested operation requires modifications in a
                        read-only file system.

     [ENAMETOOLONG]     The length of a component of a pathname is longer than
                        {NAME_MAX}.

     [EBADF]            dirfd is not a valid file descriptor.

     [ENOTDIR]          dirfd is a file descriptor associated with a non-
                        directory file.

     In addition, the fs_snapshot_create() or fs_snapshot_rename() functions
     may fail with the following errors

     [EEXIST]           The The named snapshot to be created already exists or
                        the new name already exists for the snapshot being
                        renamed.

     fs_snapshot_create() or fs_snapshot_rename() functions may fail with the
     following errors

     [ENOENT]           The named snapshot does not exist.

     fs_snapshot_delete() function may fail with

     [EBUSY]            The named snapshot is currently mounted.

SEE ALSO
     getattrlist(2), getattrlistbulk(2)

HISTORY
     The fs_snapshot_create() , fs_snapshot_delete() , fs_snapshot_delete()
     and fs_snapshot_list() function calls appeared in macOS version 10.13

Darwin                          July 4th, 2017                          Darwin