Made -boot_image isolinux activation obey -overwrite setting

libisoburn/trunk/xorriso/xorriso.1

@@ -53,6 +53,8 @@ Updates ISO subtrees incrementally to match given disk subtrees.
 Writes result either as completely new image or as add-on session
 to optical media or filesystem objects.
 .br
+Can activate ISOLINUX boot images via El Torito.
+.br
 Can perform multi-session tasks as emulation of mkisofs and cdrecord.
 .br
 Can restore files from ISO image to disk filesystem (see osirrox).
@@ -1352,39 +1354,55 @@ xorriso adds the traditional 300k of padding by default to all images.
 .br
 For images which will never get to a CD it is safe to use -padding 0 .
 .TP
+.B El Torito bootable ISO images:
+.PP
+An El Torito file object connects a boot image, which is a set of binaries
+and other files in the ISO image, with the bootstrapping facility of
+contemporary computers.
+The content of the boot image files is not in the scope of El Torito.
+.br
+Most bootable Linux CDs are equipped with ISOLINUX boot images. xorriso is
+able to create or maintain an El Torito object which makes such an image
+bootable. Emulation -as mkisofs supports the example options out of the
+ISOLINUX wiki.
+.br
+The support for other boot image types is sparse.
+.TP
 \fB\-boot_image\fR "any"|"isolinux" "discard"|"keep"|"patch"|bootspec
-Defines the handling of an eventual boot image (El-Torito) which has
+Defines the handling of an eventual El Torito object which has
 been read from an existing ISO image or defines how to make a prepared
 ISOLINUX file set bootable.
 .br
-All types ("any") of El-Torito boot images can be discarded or kept unaltered.
+
+All types ("any") of El Torito boot images can be discarded or kept unaltered.
 The latter makes only sense if the format of the boot image is
 relocatable without content changes.
 .br
-An existing boot image of type "isolinux" can be
-kept unaltered (not advisable), or be discarded, or it can be patched
-to match its relocation. In the latter case the resulting ISO image is
-bootable if the boot image was really produced by ISOLINUX.
+An existing boot image of type "isolinux" can be discarded, or it can be
+patched to match its relocation. In the latter case the resulting ISO image
+stays bootable if the boot image was really produced by ISOLINUX.
 .br
 CAUTION:
 This is an expert option. 
 xorriso cannot recognize the inner form of boot images.
 So the user has already to know about the particular needs of the
-bootimage which is present on the input media.
+boot image which is present on the input media.
 .br
 Most safe is the default: "any" "discard".
 .br
-Regardless whether an El-Torito boot image was detected or not, it is possible
+
+Regardless whether an El Torito boot image was detected or not, it is possible
 to activate a set of ISOLINUX files for booting. An existing boot image gets
 discarded, then.
-The files have to be added to the ISO image by normal means (-map, -add, ...)
-and should reside either in ISO image directory /isolinux or /boot/isolinux .
+The files have to be added to the ISO image by normal means (image loading,
+-map, -add, ...) and should reside either in ISO image directory /isolinux or
+/boot/isolinux .
 In that case it suffices to use as bootspec the text "dir=/isolinux" or
 "dir=/boot/isolinux". E.g.:
 .br
  -boot_image isolinux dir=/boot/isolinux
 .br
-It is possible to make several individual settings. E.g.
+It is possible to do this by several individual settings. E.g.
 .br
  -boot_image isolinux bin_path=/boot/isolinux/isolinux.bin
 .br
@@ -1394,9 +1412,10 @@ It is possible to make several individual settings. E.g.
 .br
 But that should hardly be necessary.
 .br
-CAUTION: xorriso only connects some ISOLINUX files to the El-Torito mechanism.
-If the ISOLINUX setup was incorrect or if the given files are not by ISOLINUX
-at all, then anything may happen when booting is attempted. 
+The El Torito object gets inserted into the ISO image at -commit time.
+Its location is the effective cat_path= .
+It is subject to normal -overwrite and -reassure processing if there is already
+a file with the same name.
 .TP
 .B Exception processing:
 .PP
@@ -1995,6 +2014,7 @@ Personality "\fBmkisofs\fR" accepts the options listed with:
 .br
 Among them: -R (always on), -J, -o, -M, -C, -path-list, -m, -exclude-list,
 -f, -print-size, -pad, -no-pad, -V, -v, -version, -graft-points,
+-no-emul-boot, -b, -c, -boot-info-table, -boot-load-size,
 pathspecs as with xorriso -add.
 A lot of options are not supported and lead to failure of the mkisofs
 emulation. Some are ignored, but better do not rely on this tolerance.
@@ -2232,6 +2252,8 @@ Manipulating an existing ISO image on the same media
 .br
 Copy modified ISO image from one media to another
 .br
+Bring a prepared ISOLINUX tree onto media and make it bootable
+.br
 Operate on storage facilities other than optical drives
 .br
 Perform multi-session runs as of cdrtools traditions
@@ -2384,6 +2406,17 @@ first and only session to the output drive.
 .br
  -commit -eject all
 .SS
+.B Bring a prepared ISOLINUX tree onto media and make it bootable
+The user has already created a suitable file tree on disk and copied the
+ISOLINUX files into subdirectory ./boot/isolinux of that tree.
+Now xorriso can burn an El Torito bootable media:
+.br
+\fB$\fR xorriso -outdev /dev/sr0 -blank as_needed \\
+.br
+   -map /home/me/ISOLINUX_prepared_tree / \\
+.br
+   -boot_image isolinux dir=/boot/isolinux
+.SS
 .B Operate on storage facilities other than optical drives
 Full read-write operation is possible with regular files and block devices:
 .br