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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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Linux Tuning The VM (memory) Subsystem

I've fast RAID-10 disk subsystem with multiple SCSI disks. Apps running under modern Linux kernel don't write directly to the disk. They write it to the file system cache which is managed by Linux kernel virtual memory manager. Since I've high performance RAID controller I need to decrease the number of flushes. How do I tune virtual memory subsystem under Linux operating systems for better performance?
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FreeBSD Set Network Polling To Boost Performance

I've Intel PRO/1000 Gigabit Ethernet adapter installed in my server. How do I set network card (NIC) polling and disable interrupts under FreeBSD operating systems to boost network performance for 100M and 1000M network links?
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FreeBSD Squid Proxy Caching Server Increase File Descriptors Limits

I'm getting an error which read as follows under FreeBSD 7.2 server and Squid stable caching server:

WARNING! Your cache is running out of filedescriptors

How do I fix this problem and increase the number of system-wide available filedescriptors for FreeBSD server?
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FreeBSD Disable Bell / Beep ( Hardware beep )

I know how to disable beep sound under Linux, but the settings are not working under FreeBSD laptop. How do I disable beep sound on FreeBSD operating system?
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FreeBSD Prevent Users From Seeing Information About Processes Owned by Other Users

Many commands accepts username and passwords on the command line and ps, top, sockstat and many commands can display this information to all users on the system. How do I prevent users from seeing information about processes that are being run under another UID to avoid information leakage under FreeBSD operating systems?
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Linux Tune Network Stack (Buffers Size) To Increase Networking Performance

I've two servers located in two different data center. Both server deals with a lot of concurrent large file transfers. But network performance is very poor for large files and performance degradation take place with a large files. How do I tune TCP under Linux to solve this problem?
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FreeBSD Jail Allow Ping / tracerouter Commands

I'm not able to ping from FreeBSD prison (jail). I'm able to resolve the names or use ftp / http for ports but ping and traceroute access is disabled. How do I allow virtualized jail application / users to perform traceroute and ping commands?
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Linux Disable Core Dumps

Only software developers legitimately need to access core files and none of my production web server requires a core dump. How do I disable core dumps on Debian / CentOS / RHEL / Fedora Linux to save large amounts of disk space?
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Linux Error: Page Allocation Failure and Solution

Q. How do I get rid of an error message that read as - "Page allocation failure"?
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