User`s guide

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Known Issues
RedHawk Linux Version 5.4 Release Notes 79
Pings to Multicast Addresses Disabled by Default
In RedHawk 4.1, a kernel.org change was imported that modified the default setting for the
sysctl flag that allows pinging to a multicast address. Where previously it was set to enable
broadcast and multicast ICMP echo (pings) and timestamp requests, it was changed to disable
that functionality.
There are two methods in which to change this flag if you need to ping multicast addresses:
• The sysctl(8) utility changes the value in a running kernel and takes effect
immediately; no rebuild or reboot is needed:
# sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=0
• To initialize the parameter to the desired value on every reboot, add the following
command and sysctl parameter to /etc/sysctl.conf:
# Controls broadcast and multicast ICMP echo and timestamp requests
net.ipv4.icmp_echo_ignore_broadcasts = 0
Grub Option Holdovers from Previous Kernel Installations
Be aware that when kernel packages are installed, they add a grub entry with options associated
with that kernel (e.g., trace and debug kernels add “crashkernel=64@48M,” other kernels add
“quiet,” etc.). In addition, all kernel packages also copy the default grub options into their grub
entries. These default grub options are taken from the kernel entry that is currently marked as
the default kernel to boot in grub.conf.
Depending upon which kernel is designated the default booting kernel and which kernels are
installed subsequently, you may find that grub entries that are inherited from the default kernel
and previously installed kernels are not suitable for the currently running kernel.
vdso and glibc 2.3.2
Changes to the location of the vdso page in the user address space in RedHawk Version 4.2 may
result in a segfault if using glibc version 2.3.2 (RedHawk 5.1, 5.2 and 5.4 use glibc 2.5).
If you are experiencing these segfaults, vdso can be disabled using the boot command vdso=0
or echo 0 > /proc/sys/vm/vdso_enabled. To determine whether you have vdso
enabled, cat /proc/1/maps and look for a vdso entry; for example:
b7f31000-b7f32000 r-xp b7f31000 00:00 0 [vdso]
USB Ports Non-functional on Supermicro Boards
Some Supermicro boards (Model X6DA8-G2, CCUR part number 820-2010483-913) may
have non-functional USB ports accompanied by the following message:
USB 1-1: new high speed USB device using ehci_hsd and address 2 USB 1-1:
device descriptor read/64, error -110
This can be corrected by changing the BIOS setting for both SATA [0/1] IDE Interface and
SCSI interface controllers to "ENABLED".