[JENKINS-50745] RHEL7's vncserver script is not compatible with the free list

Type: Bug
Resolution: Unresolved
Priority: Major
Component/s: vncviewer-plugin
Labels:
None
Environment:
RHEL7, Jenkins 2.30 and 2.66, latest version of the plugin

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The behavior of the /bin/vncserver script has changed in RHEL7: When it checks for a display to start VNC on, the code has changed:

On RHEL6, when it finds that the first display in the free list is used, it dies
On RHEL7, when it finds that the first display in the free list is used, it starts looking at display :1, bypassing the free list.

Here's the original code on RHEL7:

Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
 $displayNumber = $1;
 shift(@ARGV);
 if (!&CheckDisplayNumber($displayNumber)) {
 warn "A VNC server is already running as :$displayNumber\n";
 $displayNumber = &GetDisplayNumber();
 }
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
 &Usage();
} else {
 $displayNumber = &GetDisplayNumber();
}

Here is what we did to get it to work correctly:

Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
 $displayNumber = $1;
 shift(@ARGV);
 if (!&CheckDisplayNumber($displayNumber)) {
 die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
 }
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
 &Usage();
} else {
 $displayNumber = &GetDisplayNumber();
}

Here's the equivalent code for RHEL6:

if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
 $displayNumber = $1;
 shift(@ARGV);
 if (!&CheckDisplayNumber($displayNumber)) {
 die "A VNC server is already running as :$displayNumber\n";
 }
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
 &Usage();
} else {
 $displayNumber = &GetDisplayNumber();
}

Ugo Bellavance created issue - 2018-04-11 17:32

Ugo Bellavance made changes - 2018-04-11 17:45

Description

Original: The behavior of the /bin/vncserver script has changed in RHEL7: When it checks for a display to start VNC on, the code has changed:

* On RHEL6, when it finds that the first display in the free list is used, it dies
* On RHEL7, when it finds that the first display in the free list is used, it starts looking at display :1, bypassing the free list.

Here's the original code on RHEL6:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here is what we did to get it to work correctly:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here's the equivalent code for RHEL6:
{noformat}
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

New: The behavior of the /bin/vncserver script has changed in RHEL7: When it checks for a display to start VNC on, the code has changed:

* On RHEL6, when it finds that the first display in the free list is used, it dies
* On RHEL7, when it finds that the first display in the free list is used, it starts looking at display :1, bypassing the free list.

Here's the original code on RHEL7:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here is what we did to get it to work correctly:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here's the equivalent code for RHEL6:
{noformat}
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Ugo Bellavance made changes - 2018-04-11 17:46

Description

Original: The behavior of the /bin/vncserver script has changed in RHEL7: When it checks for a display to start VNC on, the code has changed:

* On RHEL6, when it finds that the first display in the free list is used, it dies
* On RHEL7, when it finds that the first display in the free list is used, it starts looking at display :1, bypassing the free list.

Here's the original code on RHEL7:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here is what we did to get it to work correctly:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here's the equivalent code for RHEL6:
{noformat}
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

New: The behavior of the /bin/vncserver script has changed in RHEL7: When it checks for a display to start VNC on, the code has changed:

* On RHEL6, when it finds that the first display in the free list is used, it dies
* On RHEL7, when it finds that the first display in the free list is used, it starts looking at display :1, bypassing the free list.

Here's the original code on RHEL7:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
warn "A VNC server is already running as :$displayNumber\n";
$displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here is what we did to get it to work correctly:
{noformat}
Find display number.
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
# warn "A VNC server is already running as :$displayNumber\n";
# $displayNumber = &GetDisplayNumber();
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

Here's the equivalent code for RHEL6:
{noformat}
if ((@ARGV > 0) && ($ARGV[0] =~ /^:(\d+)$/)) {
$displayNumber = $1;
shift(@ARGV);
if (!&CheckDisplayNumber($displayNumber)) {
die "A VNC server is already running as :$displayNumber\n";
}
} elsif ((@ARGV > 0) && ($ARGV[0] !~ /^-/) && ($ARGV[0] !~ /^\+/)) {
&Usage();
} else {
$displayNumber = &GetDisplayNumber();
}{noformat}

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