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sysctl command

Linux: Log Suspicious Martian Packets / Un-routable Source Addresses

I run a web-server and I would like to log packets with un-routable source addresses on Linux operating system. How can I log spoofed packets on Debian / Ubuntu / CentOS / RHEL / Linux based server? How can I log a Martian packet (packet from Mars) on Linux operating systems?
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Ubuntu Linux: Turn On Exec-Shield Buffer Overflow Protection

I am trying to set exec-shield protection on Linux as described here but getting the following error on Ubuntu Linux server version 12.04 LTS:

sysctl -w kernel.exec-shield=1
error: "kernel.exec-shield" is an unknown key

How do I fix this problem and make sure exec-shield buffer overflow protection security feature turned on Ubuntu Linux?
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Linux: Turn On TCP SYN Cookie Protection

I am under DoS attack. My cloud based server hosting company asked me to enable TCP SYN cookie protection to save my domain from SYN Attack. How do I turn on TCP Syn cookie protection under Ubuntu or CentOS Linux based server?
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FreeBSD Laptop: Find Out Battery Life Status Command

I know how to find out battery life status using Linux operating system. How do I monitor battery status on a laptop running FreeBSD version 9.x?
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I'm trying to use Cinelerra video editing and compositing software under Linux operating systems. However, I'm getting the following error:

MWindow::init_shm: /proc/sys/kernel/shmmax is 0x1000000.
It should be at least 0x7ffffff for cinelerra.

How do I fix this problem?
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Linux: Find Out Open Files [ Descriptors ] Command

How do I find out that how many files are open and how many allowed in Linux server operating systems?
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Linux: Neighbour Table Overflow Error and Solution

I setup a CentOS Linux based Linux server running as a gateway and firewall server. However, I'm getting the following messages in the /var/log/messages log file:

Dec 20 00:41:01 fw01 kernel: Neighbour table overflow.
Dec 20 00:41:01 fw01 last message repeated 20 times


Dec 20 00:41:01 fw03 kernel: [ 8987.821184] Neighbour table overflow.
Dec 20 00:41:01 fw03 kernel: [ 8987.860465] printk: 100 messages suppressed.

Why does kernel throw "Neighbour table overflow" messages in syslog? How do I fix this problem under Debian / CentOS / RHEL / Fedora / Ubuntu Linux?
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Linux Stop Flushing of mmaped Pages To Disk

How can I stop the flushing of mmaped pages to disk in Linux?
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KVM Guest: Shared Physical Network Device With Host (bridging configuration)

The NAT based connectivity is useful for easy deployments. However I want to use full bridging, where the guest is connected directly to the LAN. How do setup and share physical network with host and rest of the LAN under Linux?
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Linux Kernel /etc/sysctl.conf Security Hardening

How do I set advanced security options of the TCP/IP stack and virtual memory to improve security and performance of my system? How do I configure Linux kernel to prevent certain kinds of attacks using /etc/sysctl.conf? How do I set Linux kernel parameters?
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