The easiest way of disabling ICMP echo request on Linux is doing it on the kernel level. To disable ICMP immediately on a running system, simply enter the following command : echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all This command will not survive to the next reboot. To make it permanent, edit : vi /etc/sysctl.conf And add :… Read More »
Here is a quick how to create a dummy file for a specific size under Linux/Unix : dd if=/dev/zero of=<file_name> bs=<size_in_bytes> count=1 So assuming you want to create a file named “100mb.bin” having 100 Mb size : dd if=/dev/zero of=100mb.bin bs=104857600 count=1
If you setup OpenVPN to be in bridge (layer2) mode instead using NAT/routing (layer3) and then restart the server to make the change effective, you probably noticed the following error message on the Status Overview page repeatedly : service failed to start due to unresolved dependencies: set([‘bridge’]) This is because there is no existing bridge… Read More »
You might encountered the following message after creating a bridge interface and try to bring it up on RHEL/CentOS Linux : ifup br0 Device br0 does not seem to be present, delaying initialization. The common error in such case is usually because you mistype the ” TYPE= ” parameter, bridge must start with a… Read More »
You might noticed this error trying to log into a Linux/Unix system through SSH or SFTP : This account is currently not available. The two main possible causes : – The shell does not exist or have been removed; – Typo error when entering the shell path at the user creation. Have a look at… Read More »
Using the Windows DHCP server, you might noticed this message trying to do an IP reservation with the MAC address on your DHCP scope : The unique Identifier you have entered may not be correct. Do you want to use this Identifier anyway? And then : The DHCP server received a message from a client… Read More »
Here is a quick tutorial regarding how to install a source RPM on RHEL/CentOS Linux. 1. Prepare the build environment and get the dependencies. Do those following command under your root home directory : yum install rpm-build redhat-rpm-config gcc make mkdir -p ~/rpmbuild/{BUILD,RPMS,SOURCES,SPECS,SRPMS} 2. Put the source rpm file at the root of your home directory… Read More »
NTFS filesystem store a lot of information that might not be required all the time and can significantly improve the I/O performance when disabled, especially under a virtualized environment. To disable Last Access Time Stamp on Windows, you need to manually edit the registry. 1. Open the registry editor : Start > Run > regedit.exe 2.… Read More »
Getting this error message trying to start vsFTPd on FreeBSD? 500 OOPS: vsftpd: not configured for standalone, must be started from inetd Then you missed the important part shown at the end of “vsftpd.conf”! # If using vsftpd in standalone mode, uncomment the next two lines: listen=YES background=YES Just uncomment “listen=YES”, “background=YES” and start the… Read More »
As you might noticed on latest version of Windows, ICMP requests are blocked by default with the built-in firewall. Use this simple command to enable echo request : netsh firewall set icmpsetting 8 enable