The login to specific users can be allowed or denied using the file /etc/pam.d/remote. Other network services uses the files /etc/pam.d/sshd or /etc/pam.d/password-auth for allowing or denying the access. Whereas telnet uses the file /etc/pam.d/remote. Denying telnet login to specific users 1. Add the users you want to deny the telnet login to, in the […]
Archives for May 2018
How to Change the filesystem Labels in CentOS/RHEL
The device node name of a disk (/dev/sda, /dev/hda, /dev/vda, etc.) may change in some situations. For example, after switching cables around or upgrading certain packages, sda & sdc could swap places. This causes problems when /etc/fstab references filesystems by the disk names. Instead, we can use filesystem labels to refer them in /etc/fstab file. […]
How to change the default location (/var/cache/yum) of yum cache
The cachedir specifies the directory where yum stores downloaded packages, although with keepcache set to 0, yum does not store these packages after installing them. Consider a case where the /var filesystem where yum cache is located is full and there is no diskspace for yum to download the system updates. Also, you do not […]
How to Install and Configure Device Mapper Multipath in CentOS/RHEL 6,7
Red Hat Enterprise Linux natively supports storage that has multiple paths presented to the OS. Configuring CentOS/RHEL to use the multipath functionality is a straightforward process: Installation If not already installed, install the device-mapper-multipath package: # yum install device-mapper-multipath Location of multipath devices When devices are brought under the control of device-mapper-multipath the new multipathed […]
Understanding System Security Services Daemon (SSSD)
The System Security Services Daemon (SSSD) provides access to remote identity and authentication providers. Providers are configured as back ends with SSSD acting as an intermediary between local clients and any configured back-end provider. The local clients connect to SSSD and then SSSD contacts the providers. Benefits of SSSD include: Reduced load: Clients do not […]
How to Remove a Dead Mulitpath Device without Reboot in CentOS/RHEL
Once a multipath device is down, I/O to this device is blocked. That can cause hang when collecting a sosreport or scanning/refreshing a disk. An example of a Dead Multipath device is shown below: 360060e80166bac0000016bac000000da dm-49 HITACHI,OPEN-V size=200G features=’0′ hwhandler=’0′ wp=rw ‘-+- policy=’round-robin 0′ prio=0 status=enabled |- 8:0:0:34 sdiq 135:160 failed faulty running |- 8:0:1:34 […]
mdadm: Cannot open /dev/sda1: Device or resource busy
The Problem When trying to re-add a device to a raid, you get the following message: # mdadm /dev/md2 –add /dev/sda1 mdadm: Cannot open /dev/sda1: Device or resource busy Whereas the mdstat command indicates that the device is inactive. # cat /proc/mdstat Personalities : md2 : inactive sda1[0](S) 292928154 blocks super 1.2 unused devices: [none] […]
How to use wget to download file via proxy
The wget program allows you to download files from URLs. Although it can do a lot, the simplest form of the command is: wget [some URL]. Assuming no errors, it will place that file in the current directory. If you do not specify a filename, by default it will attempt to get the index.html file. […]
Linux Command line Basics – Working with Files and Directories
This post explains how to work with files and directories. This includes tasks, such as locating your position in the directory structure, viewing file contents, copying and moving files and directories, creating and removing files and directories, and searching for files and directories. Viewing Directories A directory is a list of references to objects, which […]
Linux Command line Basics – Executing commands from the command line
You can use system commands on the command line to instruct the system to perform specific tasks. The commands are received into a terminal window. This post is a very basic introduction to using commands with options and/or arguments and also how to run multiple commands on the command line. Note: UNIX commands are case-sensitive. […]