I need to tweak the kernel params as the Ubuntu minimal install is created for a machine with 256 MB of ram and our server has 32 GB. The issue I am having is that when I execute the command sysctl -p /etc/sysctl.conf, the server reverts back to the original settings in under a minute.
root@mino /scripts/crons/tweaks # sysctl -p /etc/sysctl.conf
vm.swappiness = 10
vm.dirty_ratio = 60
vm.dirty_background_ratio = 2
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.core.rmem_max = 12582912
net.core.rmem_default = 31457280
net.core.wmem_default = 31457280
net.core.wmem_max = 12582912
net.core.somaxconn = 4096
net.core.netdev_max_backlog = 65536
net.core.optmem_max = 25165824
net.ipv4.tcp_rfc1337 = 1
net.ipv4.ip_local_port_range = 2000 65535
net.ipv4.tcp_fin_timeout = 1
net.ipv4.tcp_max_orphans = 262144
net.ipv4.tcp_max_syn_backlog = 65535
net.ipv4.tcp_sack = 0
net.ipv4.tcp_syn_retries = 2
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_max_tw_buckets = 1440000
net.ipv4.tcp_tw_recycle = 0
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_challenge_ack_limit = 999999999
net.nf_conntrack_max = 10000000
net.netfilter.nf_conntrack_tcp_loose = 0
net.netfilter.nf_conntrack_max = 10000000
net.netfilter.nf_conntrack_tcp_timeout_close = 10
net.netfilter.nf_conntrack_tcp_timeout_close_wait = 10
net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 10
net.netfilter.nf_conntrack_tcp_timeout_last_ack = 10
net.netfilter.nf_conntrack_tcp_timeout_syn_recv = 10
net.netfilter.nf_conntrack_tcp_timeout_syn_sent = 10
net.netfilter.nf_conntrack_tcp_timeout_time_wait = 10
net.netfilter.nf_conntrack_tcp_timeout_established = 10
net.ipv4.tcp_mem = 65536 131072 262144
net.ipv4.udp_mem = 65536 131072 262144
net.ipv4.tcp_rmem = 8192 87380 16777216
net.ipv4.udp_rmem_min = 16384
net.ipv4.tcp_wmem = 8192 65536 16777216
net.ipv4.udp_wmem_min = 16384
fs.file-max = 3500000
root@mino /scripts/crons/tweaks # /sbin/sysctl -a|grep -i nf_conntrack_max
sysctl: reading key "net.ipv6.conf.all.stable_secret"
sysctl: reading key "net.ipv6.conf.default.stable_secret"
sysctl: reading key "net.ipv6.conf.em1.stable_secret"
sysctl: reading key "net.ipv6.conf.em2.stable_secret"
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
net.netfilter.nf_conntrack_max = 10000000
net.nf_conntrack_max = 10000000
root@mino /scripts/crons/tweaks # date
Sat Jan 27 08:30:50 PST 2018
root@mino /scripts/crons/tweaks # date
Sat Jan 27 08:30:57 PST 2018
root@mino /scripts/crons/tweaks # date
Sat Jan 27 08:31:02 PST 2018
root@mino /scripts/crons/tweaks # /sbin/sysctl -a|grep -i nf_conntrack_max
sysctl: reading key "net.ipv6.conf.all.stable_secret"
sysctl: reading key "net.ipv6.conf.default.stable_secret"
sysctl: reading key "net.ipv6.conf.em1.stable_secret"
sysctl: reading key "net.ipv6.conf.em2.stable_secret"
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
net.netfilter.nf_conntrack_max = 10000000
net.nf_conntrack_max = 10000000
root@mino /scripts/crons/tweaks # date
Sat Jan 27 08:31:20 PST 2018
root@mino /scripts/crons/tweaks # /sbin/sysctl -a|grep -i nf_conntrack_max
sysctl: reading key "net.ipv6.conf.all.stable_secret"
sysctl: reading key "net.ipv6.conf.default.stable_secret"
sysctl: reading key "net.ipv6.conf.em1.stable_secret"
sysctl: reading key "net.ipv6.conf.em2.stable_secret"
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
net.netfilter.nf_conntrack_max = 65536
net.nf_conntrack_max = 65536
net.nf_conntrack_max set at 65536 is too low and a simple syn attack trips the firewall and all packets are dropped. Quite annoying. I also have the same command in my /etc/rc.local fdile and read about the debian / ubuntu bug in other threads.
Running Ubuntu 14.04 4.4.0-112-generic #135-Ubuntu SMP Fri Jan 19 11:48:36 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
I did research from the following sites:
sysctl.conf - tweaking for high concurrancy & security
Linux kernel tuning settings for large number of concurrent clients
