sysctl command – nixCraft

How to prevent unprivileged users from viewing dmesg command output on Linux

June 10, 2017June 13, 2017in CentOS, Debian / Ubuntu, Linux, RedHat and Friends, Security, Suse last updated June 13, 2017

I want to restrict both normal users and root user inside LXD container “hypervisor” from viewing and using dmesg command output. How do I prevent non-root (unprivileged) Linux users from viewing the Linux kernel’s log buffer?

How to reload sysctl.conf variables on Linux

February 8, 2016in BASH Shell, CentOS, Debian / Ubuntu, Linux, Troubleshooting last updated February 8, 2016

I am new Linux system user. How do I reload all sysctl variables without rebooting my server?

FreeBSD find CPU (processor) temperature command

January 3, 2016February 24, 2017in FreeBSD, FreeBSD Jails (VPS), Hardware, UNIX last updated February 24, 2017

I‘m a new FreeBSD unix user. How do I get the temperature of an Intel or AMD processor (CPU) in FreeBSD using command line option?

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

February 19, 2014February 19, 2014in Linux, Networking, Security last updated February 19, 2014

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?

Ubuntu Linux: Turn On Exec-Shield Buffer Overflow Protection

May 19, 2013June 4, 2013in Security, Ubuntu Linux last updated June 4, 2013

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?

Linux: Turn On TCP SYN Cookie Protection

April 14, 2013in Linux, Networking, Security last updated April 14, 2013

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?

FreeBSD Laptop: Find Out Battery Life Status Command

March 13, 2013March 13, 2013in BASH Shell, FreeBSD last updated March 13, 2013

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?