LINUX system tuning record: Solves the "dstcacheoverflow" alarm Problem

LINUX system tuning record: Solves the "dstcacheoverflow" alarm problem-Linux Enterprise Application-Linux server application information. For details, see the following. OS: centos4.3

1. You can change the size of the sliding window (the default value is "1 ")

Echo "1">/proc/sys/net/ipv4/tcp_window_scaling

2. Modify the Kernel shared memory limit to 256 MB. The default value is 2 MB.

Echo 268435456>/proc/sys/kernel/shmall

Echo 268435456>/proc/sys/kernel/shmmax

3. Available proxy ports

Echo "1024 65000">/proc/sys/net/ipv4/ip_local_port_range

4. Disable broadcasting and ping.

Echo "1">/proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

Echo "1">/proc/sys/net/ipv4/icmp_ignore_bogus_error_responses

5. Change/proc/sys/net/ipv4/netfilter/ip_conntrack_max to 268435456, and the default value is 65536.

6. echo "1800">/proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_timeout_established

By default, the established connection will expire after 5 days, and will expire after half an hour, reducing the number of valid connections of ip_conntrack.

7. echo 1>/proc/sys/net/ipv4/tcp_syncookies

To prevent syn ddos attacks and enable TCPsyncookies, The CENTOS4 kernel is supported.

8. echo 2048 & gt;/proc/sys/net/ipv4/tcp_max_syn_backlog

The SYN queue length. Do not set it to too high, which will consume the corresponding memory.

9. echo 3>/proc/sys/net/ipv4/tcp_synack_retries

Number of SYN retries.

10. echo 3>/proc/sys/net/ipv4/tcp_syn_retries

Number of SYN retries.