add sysctl snippets to adjust kernel setting

Change-Id: I5acd22d8e78f94e34c246bc3b3b50c4649a80d0c

cobbler/kickstarts/default.ks

@@ -114,6 +114,12 @@ cat << EOF > /etc/security/limits.conf
 $SNIPPET('limits.conf')
 EOF
 
+cat << EOF > /etc/sysctl.conf
+$SNIPPET('sysctl.conf')
+EOF
+
+sysctl -p
+
 ## $yum_repo_stanza
 ## $yum_config_stanza
 

cobbler/snippets/sysctl.conf

@@ -0,0 +1,67 @@
+# Kernel sysctl configuration file for Red Hat Linux
+#
+# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and
+# sysctl.conf(5) for more details.
+
+# Controls IP packet forwarding
+net.ipv4.ip_forward = 0
+
+# Controls source route verification
+net.ipv4.conf.default.rp_filter = 1
+
+# Do not accept source routing
+net.ipv4.conf.default.accept_source_route = 0
+
+# Controls the System Request debugging functionality of the kernel
+kernel.sysrq = 0
+
+# Controls whether core dumps will append the PID to the core filename.
+# Useful for debugging multi-threaded applications.
+kernel.core_uses_pid = 1
+
+# Controls the use of TCP syncookies
+net.ipv4.tcp_syncookies = 1
+
+# Controls the default maxmimum size of a mesage queue
+kernel.msgmnb = 65536
+
+# Controls the maximum size of a message, in bytes
+kernel.msgmax = 65536
+
+# Controls the maximum shared segment size, in bytes
+kernel.shmmax = 68719476736
+
+# Controls the maximum number of shared memory segments, in pages
+kernel.shmall = 4294967296
+
+# increase TCP max buffer size settable using setsockopt()
+net.core.rmem_max = 16777216
+net.core.wmem_max = 16777216 
+
+# increase Linux autotuning TCP buffer limit 
+net.ipv4.tcp_rmem = 4096 87380 16777216
+net.ipv4.tcp_wmem = 4096 65536 16777216
+
+# increase the length of the processor input queue
+net.core.netdev_max_backlog = 30000
+net.ipv4.tcp_max_syn_backlog = 4096
+
+# recommended default congestion control is htcp 
+net.ipv4.tcp_congestion_control=htcp
+
+# recommended for hosts with jumbo frames enabled
+net.ipv4.tcp_mtu_probing=1
+
+# increase client parallel connections
+net.ipv4.ip_local_port_range = 15000 61000
+net.ipv4.tcp_fin_timeout=30
+
+# fast cycling of sockets in time_wait state and re-using them
+net.ipv4.tcp_tw_recycle = 1
+net.ipv4.tcp_tw_reuse = 1 
+
+# increase the maximum number of requests queued to a listen socket
+net.core.somaxconn = 1024
+
+# avoid caching tcp network transfer statistics 
+net.ipv4.route.flush=1