Clarify sparse behaviour of truncate-size command.

[libguestfs.git] / src / generator.ml

diff --git a/src/generator.ml b/src/generator.ml
index f094749..99d80fb 100755 (executable)
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -3152,7 +3152,7 @@ Unknown file type
 
 =item '?'
 
-The L<readdir(3)> returned a C<d_type> field with an
+The L<readdir(3)> call returned a C<d_type> field with an
 unexpected value
 
 =back
@@ -3475,7 +3475,7 @@ The C<-f> option removes the link (C<linkname>) if it exists already.");
    "\
 This command reads the target of a symbolic link.");
 
-  ("fallocate", (RErr, [Pathname "path"; Int "len"]), 169, [],
+  ("fallocate", (RErr, [Pathname "path"; Int "len"]), 169, [DeprecatedBy "fallocate64"],
    [InitBasicFS, Always, TestOutputStruct (
       [["fallocate"; "/a"; "1000000"];
        ["stat"; "/a"]], [CompareWithInt ("size", 1_000_000)])],
@@ -3797,8 +3797,8 @@ was built (see C<appliance/kmod.whitelist.in> in the source).");
     )],
    "echo arguments back to the client",
    "\
-This command concatenate the list of C<words> passed with single spaces between
-them and returns the resulting string.
+This command concatenates the list of C<words> passed with single spaces
+between them and returns the resulting string.
 
 You can use this command to test the connection through to the daemon.
 
@@ -3925,8 +3925,13 @@ file must exist already.");
    "truncate a file to a particular size",
    "\
 This command truncates C<path> to size C<size> bytes.  The file
-must exist already.  If the file is smaller than C<size> then
-the file is extended to the required size with null bytes.");
+must exist already.
+
+If the current file size is less than C<size> then
+the file is extended to the required size with zero bytes.
+This creates a sparse file (ie. disk blocks are not allocated
+for the file until you write to it).  To create a non-sparse
+file of zeroes, use C<guestfs_fallocate64> instead.");
 
   ("utimens", (RErr, [Pathname "path"; Int64 "atsecs"; Int64 "atnsecs"; Int64 "mtsecs"; Int64 "mtnsecs"]), 201, [],
    [InitBasicFS, Always, TestOutputStruct (
@@ -4036,7 +4041,7 @@ C<names> is the list of files from this directory.
 
 On return you get a list of strings, with a one-to-one
 correspondence to the C<names> list.  Each string is the
-value of the symbol link.
+value of the symbolic link.
 
 If the C<readlink(2)> operation fails on any name, then
 the corresponding result string is the empty string C<\"\">.
@@ -4711,7 +4716,7 @@ This command is the same as C<guestfs_ntfsresize> except that it
 allows you to specify the new size (in bytes) explicitly.");
 
   ("available_all_groups", (RStringList "groups", []), 251, [],
-   [],
+   [InitNone, Always, TestRun [["available_all_groups"]]],
    "return a list of all optional groups",
    "\
 This command returns a list of all optional groups that this
@@ -4722,6 +4727,28 @@ returned list.
 
 See also C<guestfs_available> and L<guestfs(3)/AVAILABILITY>.");
 
+  ("fallocate64", (RErr, [Pathname "path"; Int64 "len"]), 252, [],
+   [InitBasicFS, Always, TestOutputStruct (
+      [["fallocate64"; "/a"; "1000000"];
+       ["stat"; "/a"]], [CompareWithInt ("size", 1_000_000)])],
+   "preallocate a file in the guest filesystem",
+   "\
+This command preallocates a file (containing zero bytes) named
+C<path> of size C<len> bytes.  If the file exists already, it
+is overwritten.
+
+Note that this call allocates disk blocks for the file.
+To create a sparse file use C<guestfs_truncate_size> instead.
+
+The deprecated call C<guestfs_fallocate> does the same,
+but owing to an oversight it only allowed 30 bit lengths
+to be specified, effectively limiting the maximum size
+of files created through that call to 1GB.
+
+Do not confuse this with the guestfish-specific
+C<alloc> and C<sparse> commands which create
+a file in the host and attach it as a device.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions