procps/sysctl.conf

#
# Distribution defaults.
# Use /etc/sysctl.conf to override.
#
# Disable response to broadcast pings to avoid smurf attacks.
net.ipv4.icmp_echo_ignore_broadcasts = 1

# enable route verification on all interfaces
net.ipv4.conf.all.rp_filter = 1

# avoid deleting secondary IPs on deleting the primary IP
net.ipv4.conf.default.promote_secondaries = 1
net.ipv4.conf.all.promote_secondaries = 1

# disable IPv6 completely
#net.ipv6.conf.all.disable_ipv6 = 1

# enable IPv6 forwarding
#net.ipv6.conf.all.forwarding = 1

# enable IPv6 privacy (bnc#678066)
net.ipv6.conf.default.use_tempaddr = 2

# increase the number of possible inotify(7) watches
fs.inotify.max_user_watches = 65536

# Magic SysRq Keys enable some control over the system even if it
# crashes (e.g. during kernel debugging).
#
#   0 - disable sysrq completely
#   1 - enable all functions of sysrq
#  >1 - bitmask of allowed sysrq functions:
#          2 - enable control of console logging level
#          4 - enable control of keyboard (SAK, unraw)
#          8 - enable debugging dumps of processes etc.
#         16 - enable sync command
#         32 - enable remount read-only
#         64 - enable signalling of processes (term, kill, oom-kill)
#        128 - allow reboot/poweroff
#        256 - allow nicing of all RT tasks
#
# For further information see /usr/src/linux/Documentation/sysrq.txt
# default 176 = 128+32+16
kernel.sysrq = 176