Frequently Asked Questions About Linux / UNIX » /etc/sysctl.conf http://www.cyberciti.biz/faq Every answer asks a more beautiful question. Fri, 03 Feb 2012 22:38:32 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 Linux: Find Out Open Files [ Descriptors ] Commandhttp://www.cyberciti.biz/faq/linux-find-total-open-files-descriptors/ http://www.cyberciti.biz/faq/linux-find-total-open-files-descriptors/#comments Wed, 04 Jan 2012 18:25:02 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11334 How do I find out that how many files are open and how many allowed in Linux server operating systems?]]> http://www.cyberciti.biz/faq/linux-find-total-open-files-descriptors/feed/ 2 Linux: Neighbour Table Overflow Error and Solutionhttp://www.cyberciti.biz/faq/centos-redhat-debian-linux-neighbor-table-overflow/ http://www.cyberciti.biz/faq/centos-redhat-debian-linux-neighbor-table-overflow/#comments Mon, 19 Dec 2011 19:39:11 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11265 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
OR
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?]]> http://www.cyberciti.biz/faq/centos-redhat-debian-linux-neighbor-table-overflow/feed/ 0 Linux Stop Flushing of mmaped Pages To Diskhttp://www.cyberciti.biz/faq/linux-stop-flushing-of-mmaped-pages-to-disk/ http://www.cyberciti.biz/faq/linux-stop-flushing-of-mmaped-pages-to-disk/#comments Sat, 01 Jan 2011 20:33:17 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10036 How can I stop the flushing of mmaped pages to disk in Linux?]]> http://www.cyberciti.biz/faq/linux-stop-flushing-of-mmaped-pages-to-disk/feed/ 0 FreeBSD: Disable / Stop Console Beep ( Bell )http://www.cyberciti.biz/faq/freebsd-stop-console-terminal-beep-bell/ http://www.cyberciti.biz/faq/freebsd-stop-console-terminal-beep-bell/#comments Wed, 21 Jul 2010 01:45:01 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8485 I know how to turn off console beep under Gnome Linux desktop. How do I stop console beep under FreeBSD operating systems?]]> http://www.cyberciti.biz/faq/freebsd-stop-console-terminal-beep-bell/feed/ 0 Linux Kernel /etc/sysctl.conf Security Hardeninghttp://www.cyberciti.biz/faq/linux-kernel-etcsysctl-conf-security-hardening/ http://www.cyberciti.biz/faq/linux-kernel-etcsysctl-conf-security-hardening/#comments Tue, 27 Oct 2009 16:55:00 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5564 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? ]]> http://www.cyberciti.biz/faq/linux-kernel-etcsysctl-conf-security-hardening/feed/ 2 Linux Tuning The VM (memory) Subsystemhttp://www.cyberciti.biz/faq/linux-kernel-tuning-virtual-memory-subsystem/ http://www.cyberciti.biz/faq/linux-kernel-tuning-virtual-memory-subsystem/#comments Fri, 16 Oct 2009 09:29:09 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5366 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?]]> http://www.cyberciti.biz/faq/linux-kernel-tuning-virtual-memory-subsystem/feed/ 5 FreeBSD Set Network Polling To Boost Performancehttp://www.cyberciti.biz/faq/freebsd-device-polling-network-polling-tutorial/ http://www.cyberciti.biz/faq/freebsd-device-polling-network-polling-tutorial/#comments Tue, 23 Jun 2009 00:30:33 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4163 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?]]> http://www.cyberciti.biz/faq/freebsd-device-polling-network-polling-tutorial/feed/ 5 FreeBSD Squid Proxy Caching Server Increase File Descriptors Limitshttp://www.cyberciti.biz/faq/squid-increase-file-descriptors-limits-under-freebsd/ http://www.cyberciti.biz/faq/squid-increase-file-descriptors-limits-under-freebsd/#comments Thu, 18 Jun 2009 17:56:03 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4122 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?]]> http://www.cyberciti.biz/faq/squid-increase-file-descriptors-limits-under-freebsd/feed/ 1 FreeBSD Disable Bell / Beep ( Hardware beep )http://www.cyberciti.biz/faq/turning-off-freebsd-system-hardware-beep-linux/ http://www.cyberciti.biz/faq/turning-off-freebsd-system-hardware-beep-linux/#comments Sat, 06 Jun 2009 12:35:11 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3982 I know how to disable beep sound under Linux, but the settings are not working under FreeBSD laptop. How do I disable beep sound under FreeBSD operating system?]]> http://www.cyberciti.biz/faq/turning-off-freebsd-system-hardware-beep-linux/feed/ 4 FreeBSD Prevent Users From Seeing Information About Processes Owned by Other Usershttp://www.cyberciti.biz/faq/freebsd-disable-ps-sockstat-command-information-leakage/ http://www.cyberciti.biz/faq/freebsd-disable-ps-sockstat-command-information-leakage/#comments Mon, 25 May 2009 14:04:58 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3849 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? ]]> http://www.cyberciti.biz/faq/freebsd-disable-ps-sockstat-command-information-leakage/feed/ 9 Linux Tune Network Stack (Buffers Size) To Increase Networking Performancehttp://www.cyberciti.biz/faq/linux-tcp-tuning/ http://www.cyberciti.biz/faq/linux-tcp-tuning/#comments Wed, 20 May 2009 09:21:32 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3820 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?]]> http://www.cyberciti.biz/faq/linux-tcp-tuning/feed/ 20 FreeBSD Jail Allow Ping / tracerouter Commandshttp://www.cyberciti.biz/faq/freebsd-jail-allow-ping-tracerouter-commands/ http://www.cyberciti.biz/faq/freebsd-jail-allow-ping-tracerouter-commands/#comments Sat, 09 May 2009 12:55:04 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3763 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? ]]> http://www.cyberciti.biz/faq/freebsd-jail-allow-ping-tracerouter-commands/feed/ 0 Linux Disable Core Dumpshttp://www.cyberciti.biz/faq/linux-disable-core-dumps/ http://www.cyberciti.biz/faq/linux-disable-core-dumps/#comments Thu, 26 Feb 2009 13:38:21 +0000 Vivek Gite /dev/null 2>&1]]> http://www.cyberciti.biz/faq/?p=3392 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?]]> http://www.cyberciti.biz/faq/linux-disable-core-dumps/feed/ 4 Linux Error: Page Allocation Failure and Solutionhttp://www.cyberciti.biz/faq/linux-page-allocation-failure-erro/ http://www.cyberciti.biz/faq/linux-page-allocation-failure-erro/#comments Thu, 25 Sep 2008 09:07:02 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=1889 Q. How do I get rid of an error message that read as - "Page allocation failure"?]]> http://www.cyberciti.biz/faq/linux-page-allocation-failure-erro/feed/ 0 CentOS / Red Hat Linux IP Forwarding How Tohttp://www.cyberciti.biz/faq/rhel-centos-fedora-linux-ip-forwarding-tutorial/ http://www.cyberciti.biz/faq/rhel-centos-fedora-linux-ip-forwarding-tutorial/#comments Sat, 05 Jul 2008 15:25:00 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4344 How do I enable IP forwarding under RHEL / Red Hat / Fedora / CentOS Linux operating systems?]]> http://www.cyberciti.biz/faq/rhel-centos-fedora-linux-ip-forwarding-tutorial/feed/ 0 Linux Increase The Maximum Number Of Open Files / File Descriptors (FD)http://www.cyberciti.biz/faq/linux-increase-the-maximum-number-of-open-files/ http://www.cyberciti.biz/faq/linux-increase-the-maximum-number-of-open-files/#comments Tue, 18 Apr 2006 15:56:00 +0000 Vivek Gite http://www.cyberciti.biz/faq/faq/linux-increase-the-maximum-number-of-open-files.php How do I increase the maximum number of open files under CentOS Linux? How do I open more file descriptors under Linux?]]> http://www.cyberciti.biz/faq/linux-increase-the-maximum-number-of-open-files/feed/ 37