Archives for September 2018

The Problem While executing yum commands user is getting below error: # yum update Bad id for repo: My Repo, byte = 2 The following is the repo file which is used for local dvd image # cat /etc/yum.repos.d/my_repo.repo [My Repo] name=repo1 baseurl=file:///mnt/iso/ enabled=1 gpgcheck=0 The Solution [My Repo] is wrong as it uses spaces between letters which are not properly translated by yum. Do not include white space in [My Repo]. So to correct it change the name file from … [Read more...] about “Bad id for repo: My Repo, byte = 2” yum update error

What is lvmetad To improve performance and automatic activation of volume groups and logical volumes by udev, LVM makes use of a metadata cache. By default, LVM manages its metadata centrally using a daemon, lvmetad. How to disable lvmetad Sometimes, especially in a clustered environment, you may find that when you create a volume group on one node of the cluster, the same is not reflected on the other nodes of the cluster. This is mainly due to the cached metadata on the other nodes. Some … [Read more...] about How to disable lvmetad in CentOS/RHEL

Sometimes for the security reasons, there is a need to have a separate port for ssh and sftp on CentOS/RHEL. Here's a short how-to on configuring SSH on port 2222 and SFTP to work on port 22. 1. Since openssh-5.3p1-117.el6.x86_64 for separating the ssh and sftp port on the CentOS/RHEL systems, make changes to the /etc/ssh/sshd_config file and add the following modifications. # vi /etc/ssh/sshd_config Port 22 Port 2222 2. Comment the default subsystem and add the below subsystem. # vi … [Read more...] about How to Configure Separate Port For SSH and SFTP On CentOS/RHEL

To modify the telnet timeout you need to change the value of the tcp keepalive parameters. Let us first check the default values of TCP keepalive parameter. # cat /proc/sys/net/ipv4/tcp_keepalive_time 7200 # cat /proc/sys/net/ipv4/tcp_keepalive_intvl 75 # cat /proc/sys/net/ipv4/tcp_keepalive_probes 9 The first two parameters are expressed in seconds, and the last is the pure number. This means that the keepalive routines wait for two hours (7200 secs) before sending the first keepalive … [Read more...] about How to Change the Default Timeout Settings for Telnet Session in CentOS/RHEL

Follow steps below to check and change the default port (161) number on which snmp service would be listening. NOTE: Similarly for each service there will be a port over which the service is binded to. There is a common miss conception that the port mapping is done over /etc/services file. This is just an alias mapping for the users to refer when connecting across the network. A protocol mapped again the port in the /etc/services file does not mean that the port is blocked or unblocked by a … [Read more...] about How to modify snmp service to listen to an alternative port in CentOS/RHEL

The Linux ssh server never disconnects ssh session from server side by default, check switch/router/firewall configuration to avoid the issue without changing the configuration of ssh servers/clients. If the ssh session is getting disconnected due to inactivity and one wants to stop this then please follow the below steps either on client or server side as described below: Client Side Settings To enable the keep alive system-wide (root access required), edit the configuration file … [Read more...] about How to Stop SSH Session From Getting Timed Out

This post will provide details on TCP connections reporting 'CLOSE_WAIT' states. The possible state values for TCP sockets are as follows: BOUND        Bound, ready to connect or listen. CLOSED       Closed. The socket is not being used. CLOSING      Closed, then remote shutdown; awaiting acknowledgment. CLOSE_WAIT   Remote shutdown; waiting for the socket to close. ESTABLISHED  Connection has been established. FIN_WAIT_1   Socket closed; shutting down connection. … [Read more...] about Why Does “netstat” Output Show Many Connections in CLOSE_WAIT Status?