Cannot start VM with error “no network with matching name ‘default'”

I update libvirt version and want to start VM with the new libvirt tools but I failed as follows. > sudo virsh start kvm1 error: Failed to start domain kvm1 error: Network not found: no network with matching name ‘default’ It seems that the default ‘virbr0’ is missing after I update libvirt so I solve […]

How to log connections hitting certain rules in iptables on Linux?

How to log connections hitting certain rules in iptables on Linux? Like the one that are dropped because of too frequently creating SSH connections. You can create a new chain named LOGNDROP that log the connections and drop them, then pass the connection to be redirected to the LOGNDROP chain. $tables -N LOGNDROP # Connections […]

How to use iptables to limit rates new SSH incoming connections from each IP on Linux?

How to use iptables to limit rates new SSH incoming connections from each IP on Linux? For example, at most 6 SSH connection attempts every 60 seconds. You may use these rules (skip the first one, if you have set the basic rules): for tables in iptables ip6tables ; do # Allow established inbound connections […]

How to configure iptables on Linux Mint 17.1?

How to configure iptables and make the configuration persistent across system restarting on Linux Mint 17.1? You can use the ‘iptables-persistent’ tool. To install iptables-persistency pachage: sudo aptitude install iptables-persistent The you can manipulate the iptables by the ‘iptables’ command. To save the current iptables rules: sudo /etc/init.d/iptables-persistent store It will store the rules for […]

How to enable iptables on CentOS 7 / Fedora 20?

iptables is plain old good. How to enable it after I disable firewalld? First, install the iptables-services package as root: # yum install iptables-services Then, start iptables service as root: # touch /etc/sysconfig/iptables # touch /etc/sysconfig/ip6tables # systemctl start iptables # systemctl start ip6tables # systemctl enable iptables # systemctl enable ip6tables Answered by Eric […]

Where are the Linux routing table entries stored on disk?

I know the routing tables on Linux is in memory after being set. However, where are the routing table entries stored on disk? I mean where are the routing table is persistently stored so that the routing table can be reloaded like the iptables (under /etc/sysconfig/iptables on Fedora/RHEL/CentOS Linuxes). If the system uses the /etc/rc.d/init.d/network […]

Directly SSH to Hosts’ Internal IPs Through the Gateway

We have many hosts with internal/LAN IPs like 10.0.3.* behind a gateway and the hosts with LAN IPs can connect to the Internet through the gateway. We used iptables to forward port from the gateway to internal IPs so that users from hosts with Internet connections can SSH to the gateway’s forwarded port to log […]

Setting Up VPN-like Network Between Several Clusters Using iptables

It is common to connect servers with only internal IPs from several clusters. VPN is a common technique for this. With iptables, we can implement many functions of VPN with possibly higher performance. The slides here give a brief introduction to how to set up a VPN-like network between 2 clusters which connect to each […]

Linux Cluster Solutions

Solutions to Linux cluster construction and management such as unified account management, NFS home directory, network configurations are summarised in this post. The post is keeping updating while new solutions is added to this site. Account and storage management ∞ Unified Linux Login and Home Directory Using OpenLDAP and NFS/automount Backup Linux Home Directory Using […]

Hadoop Installation Tutorial (Hadoop 1.x)

Update: If you are new to Hadoop and trying to install one. Please check the newer version: Hadoop Installation Tutorial (Hadoop 2.x). Hadoop mainly consists of two parts: Hadoop MapReduce and HDFS. Hadoop MapReduce is a programming model and software framework for writing applications, which is an open-source variant of MapReduce that is initially designed […]