Testing the following (uncommon) syslinux.cfg with different Syslinux
versions allows getting to several observations; some might be of
interest to users, and some for the Syslinux developers.
syslinux.cfg
***
UI menu.c32
DEFAULT help
TIMEOUT 30
# ONTIMEOUT help
LABEL pwd
COM32 pwd.c32
LABEL help
MENU HELP help.txt
***
1_ For the TIMEOUT-related directives to behave as expected, at least
2 LABELs shall be present.
2_ Manually selecting "LABEL help" from the menu will display the
content of "help.txt".
3_ Letting the DEFAULT or the ONTIMEOUT (when uncommented) directives
automatically select "LABEL help" means that the core (not menu.c32)
parses the "MENU HELP" directive, which of course fails (since the
core parses MENU directives as comments, or disregards them, or does
not understand them). The following tests take advantage of this
known behavior so to trigger error messages.
4_ Using Syslinux 4.05 with the above cfg:
4.1_ The menu is displayed for 3 seconds; and then;
4.2_ An error message, "Invalid or corrupt kernel image", and the
"boot:" prompt are displayed; and then;
4.3_ After 3 additional seconds the menu is displayed again (as the
UI directive takes precedence).
4.4_ This whole cycle repeats itself until user intervention.
5_ Using Syslinux 4.05 with the above cfg but with ONTIMEOUT
uncommented:
5.1_ The menu is displayed for 3 seconds; and then;
5.2_ An error message, "Invalid or corrupt kernel image", and the
"boot:" prompt are displayed; and then;
5.3_ After 3 additional seconds, a _different_ error message, "Could
not find kernel image: help", is displayed followed by the
"boot:"
prompt; and then;
5.4_ The step above, #5.3 alone, repeats itself until user
intervention.
Observation #5.1: In Syslinux 4.05, once in CLI mode, the ONTIMEOUT
directive takes precedence over the UI directive.
Observation #5.2: In this case ("ONTIMEOUT + MENU HELP help.txt"),
there are 2 different error messages, depending on whether the menu
or the CLI is used.
6_ Repeating test #4, with the above cfg but using Syslinux
6.03-pre10:
6.1_ The menu is displayed for 3 seconds; and then;
6.2_ No error message is visible. The menu is displayed again, for
the next 3 seconds, and the cycle repeats itself until user
intervention.
6.3_ Pressing ESC twice we end up in the "boot:" prompt (first ESC)
and the timer has no effect now (after the second ESC).
6.4_ Entering "help" in CLI we trigger the "LABEL help"
entry. Since
the CLI cannot parse a "MENU HELP help.txt" directive, we get a
"Loading help... failed: No such file or directory", followed by the
"boot:" prompt.
6.5_ After 3 seconds, the TIMEOUT directive kicks in, displaying the
menu (again).
6.6_ Repeat step #6.3.
6.7_ Repeat step #6.4 but after the error message is displayed we
press ESC once more, so the TIMEOUT is stopped, leaving us in the
"boot:" prompt, where we can clearly still see the error message from
attempting the "LABEL help" entry from CLI.
Observation #6.1: Note the different behavior comparing step #4.2
with step #6.2.
Observation #6.2: In Syslinux 4.05, the error message is "Invalid or
corrupt kernel image", while in Syslinux 6.03-pre10 the error message
is "Loading help... failed: No such file or directory" (where
"help"
is the name of the "kernel image").
Observation #6.3: In Syslinux 4.05, the error message is visible,
while in Syslinux 6.03-pre10 the error message might not be. In
Syslinux 6.03-pre10, the behavior that a common user would see is
just the menu being displayed again and again. In such condition, a
user would need to know how to trigger a relevant error message from
CLI.
7_ *Attempting* to repeat test #5, with the above cfg but with
ONTIMEOUT uncommented, using Syslinux 6.03-pre10:
7.1_ The menu is displayed for 3 seconds; and then it is displayed
again and again. At this point, the behavior is already different
between Syslinux 4.05 and 6.03-pre10.
7.2_ Press ESC once, so to get to CLI. After the TIMEOUT (3 seconds),
an error message, "Loading help... failed: No such file or directory"
(where "help" is the "kernel image"), followed by the
"boot:" prompt;
and then;
7.3_ After 3 additional seconds, the _same_ error message, "Loading
help... failed: No such file or directory", is displayed followed by
the "boot:" prompt; and then;
7.4_ The step above, #7.3 alone, repeats itself until user
intervention.
Observation #7.1: Note the different behavior comparing step #5.2
with step #7.1.
Observation #7.2: In Syslinux 6.03-pre10 (same as in Syslinux 4.05),
once in CLI mode, the ONTIMEOUT directive takes precedence over the
UI directive.
Observation #7.3: In Syslinux 6.03-pre10 the error message is the
same, whether the error is triggered by the menu parser or by the
core. In Syslinux 4.05 the respective error messages were different.
8_ Testing the behavior of the SHIFT / ALT / CAPS LOCK / SCROLL LOCK
keys during boot time (so to bypass the default "PROMPT 0") in
Syslinux 4.05, the expected behavior is seen: instead of booting into
the menu (UI directive), we boot into the "boot:" prompt.
9_ Testing the behavior of the SHIFT / ALT / CAPS LOCK / SCROLL LOCK
keys during boot time (so to bypass the default "PROMPT 0") in
Syslinux 6.03-pre10, all alternative keys fail. This bug is present
since version 5.00. Note that I have not tested the "MENU SHIFTKEY"
behavior, which is a different feature.
To be clear, I am not saying that the current behaviors are a problem
(except for the last test #9); I am just pointing them out.
Hopefully this email might be of interest for some user(s). In some
cases, users might just see a menu displayed again and again,
covering up relevant error messages. In the future, web search
engines might consider the Syslinux Mailing List as "active" again
(as oppose to the current erroneous "dormant" state). Perhaps some
documentation improvements could result from this. The behaviors
described here might eventually catch the attention of the Syslinux
developers, perhaps in relation to some (future) report. And perhaps
the current bug in the "force-boot-prompt keys" could be resolved.
Regards,
Ady.
