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 LVM can optionally use a central metadata cache, implemented through a daemon (lvmetad) and a udev rule. The metadata daemon has two main purposes: it improves the performance of LVM commands and it allows udev to automatically activate logical volumes or entire volume groups as they become available to the system. How to disable lvmetad You may sometime experience that LVM changes are not reflected by the rest of the nodes in your cluster. After creating a volume group on a … [Read more...] about How to disable lvmetad in CentOS/RHEL

As per package description, RealtimeKit is a D-Bus system service that changes the scheduling policy of user processes/threads to SCHED_RR (i.e. real-time scheduling mode) on request. It is intended to be used as a secure mechanism to allow real-time scheduling to be used by normal user processes. Command "rpm -q --whatrequires rtkit" will list all the rpm packages installed on the system which requires rtkit. # rpm -q --whatrequires rtkit pulseaudio-10.0-5.el7.x86_64 If there is no … [Read more...] about How to disable rtkit-daemon in CentOS/RHEL

The Ask The customer wants to disable SSH login and only enable rsync to transfer data. The Solution It is possible to allow rsync and disable ssh by configuring rsync in daemon mode. In order to achieve this below steps can be performed. 1. Configure rsync in daemon mode in server. For this we need to first modify file /etc/rsyncd.conf, the following is an example: # vi /etc/rsyncd.conf motd file = /etc/rsyncd.motd log file = /var/log/rsyncd.log pid file = /var/run/rsyncd.pid lock … [Read more...] about How to configure rsysnc in daemon mode (allow rsync and disable SSH login) in CentOS/RHEL

The Ask The client wants to disable the MOTD or the banner message to be disabled only for a specific user in CentOS/RHEL 7. How can we disable the banner message for ssh/sftp in this case just for a specific user? The Solution As per the SSH confiugration /etc/ssh/sshd_config, one can override the golbal/default settings. Here is a snippet from the file. # cat /etc/ssh/sshd_config ... # Example of overriding settings on a per-user basis # Match User anoncvs # X11Forwarding … [Read more...] about How to set/disable banner message (MOTD) for a specific user in CentOS/RHEL

If you are a Linux system admin you must have dealt with at least one of the shell profile files from below list in your life. /etc/profile /etc/bashrc ~/.profile ~/.bash_profile ~/.bashrc ~/.kshrc These files are called the shell profile files and as the name suggests they are basically used to set the environment in a specific shel. So if you want to set some variable in ksh shell, you must include that variable in ~/.kshrc file. These file resides in the home directory of the local … [Read more...] about Understanding shell profiles in CentOS/RHEL

Red Hat Enterprise Linux provides several ways to display which commands were run before the server reboots; psasct and lastcomm to name the important ones. lastcomm prints out information about previously executed commands. If no arguments are specified, lastcomm will print info about all of the commands in acct (the record file). Installing psacct (process accounting) The psacct service is responsible for starting and stopping process accounting at system boot time and at system shutdown. … [Read more...] about How to find the commands run by user before reboot in CentOS/RHEL

The psacct service is responsible for starting and stopping process accounting at system boot time and at system shutdown. This service is a wrapper that invokes the accton accounting control program. A user may need to collect process accounting data to better understand which commands were executed on a system. The file /var/account/psacct is where all process accounting data is logged. The file can not be read directly and we need to use the command "strings" to read the … [Read more...] about How to Start/Stop and Enable/Disable process accounting (psacct)

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