The Geek Diary

CentOS/RHEL 7

‘error opening class fc_host’ – systool Command Error on CentOS/RHEL 7 and 8

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The Problem When running the systool command on CentOS/RHEL 7, the following error message is reported: # systool -c fc_host -v Error opening class fc_host The Solution The error occurs because the scsi_transport_fc module that is responsible for populating the contents of /sys/class/fc_host/ directory is not loaded on the system. 1. Manually load the scsi_transport_fc […]

Dependency failed for NFS server and services

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The Problem Attempting to start the NFS (nfs-server.service) on CentOS/RHEL 7 fails as follows: # systemctl status nfs-server.service nfs-server.service – NFS server and services Loaded: loaded (/usr/lib/systemd/system/nfs-server.service; enabled; vendor preset: disabled) Drop-In: /run/systemd/generator/nfs-server.service.d ‘-order-with-mounts.conf Active: inactive (dead) Mar 09 16:17:10 hostname systemd[1]: Dependency failed for NFS server and services. Mar 09 16:17:10 hostname systemd[1]: nfs-server.service: […]

“cannot install the best update candidate for package” – error on running dnf update

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The Problem Running the ‘dnf update’ command fails with below error: # dnf update Error: Problem 1: package perl-4:5.26.3-419.el8.x86_64 requires perl-interpreter(x86-64) = 4:5.26.3-419.el8, but none of the providers can be installed – cannot install both perl-interpreter-4:5.26.3-419.el8_4.1.x86_64 and perl-interpreter-4:5.26.3-419.el8.x86_64 – cannot install the best update candidate for package perl-interpreter-4:5.26.3-419.el8.x86_64 – cannot install the best update candidate […]

How To Configure sssd To Work With Multiple Active Directory Domains in Different Forests (CentOS/RHEL)

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This post describes an approach to configuring sssd in order to interact with multiple Active Directory Domains located in different forests. This method involves altering /etc/krb5.conf and /etc/sssd/sssd.conf files. 1. Join the first domain (domain1.com) from the first forest. # realm join –verbose domain1.com -U LinuxAD@DOMAIN1.COM 2. Edit /etc/krb5.conf file and add the secondary domain […]

“error: Bind to port 2222 on 0.0.0.0 failed: Permission denied” – error while starting sshd service on CentOS/RHEL

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The Problem On CentOS/RHEL, the OpenSSH SSH Daemon (sshd) utilizes port 22 for incoming connection requests from remote OpenSSH SSH (ssh) and Secure File Transfer (sftp) clients. In some cases, however, System Administrators prefer to utilize separate ports to service ssh and sftp activity. In One such case, system administrator is facing below error while […]

Configure MySQL Router to Auto Restart of Failure using systemd

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The systemd unit file that ships with the MySQL Router 8.0 RPM’s will not automatically restart mysqlrouter on failure. It can be modifed to do so, though, by editing the file /usr/lib/systemd/system/mysqlrouter.service and adding this line: Restart=on-failure Put it right after the “ExecStart” line, so that the file ooks like this: [Unit] Description=MySQL Router After=syslog.target […]

How To Enforce Password Complexity For All Users, Including “root”, By Using the “passwdqc” PAM Module CentOS/RHEL

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This post outlines steps to configure password complexity for all the users, including root. The “pam_cracklib.so” PAM module does not check the password complexity for the “root” user by default. So to overcome that the “pam_passwdqc.so” module can be used to apply the restrictions for all the users, including “root”. 1. “pam_passwdqc.so” is provided by […]

PAM password complexity and pam_cracklib credit system in CentOS/RHEL

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This post describes the PAM pam_cracklib credit system in relation to Linux PAM password complexity. Overview of PAM The Pluggable Authentication Modules (PAM) is a central, flexible, modular framework used to manage system authentication policies and facilitate user authentication. PAM provides a general Application Programming Interface (API) that privilege granting programs defer to for user […]