CentOS/RHEL 6

Introduction If you are using old software on new software you can receive some weird errors. Today We will describe an error with Inle l219-LM and CentOS 6 error. For some reason from time to time, Centos 6 fails to start network when using the Intel I219-LM network card. We’ve faced the following issue with […]

Question: How to confgure ssh to run on 2 ports i.e. 22 and 2222. There may be requirements as such above in some environments to run ssh on multiple ports. Well this can be achieved by modifying the /etc/ssh/sshd_config configuration file. The stpes are outlined as below: 1. Edit the sshd configuration file /etc/ssh/sshd_config # […]

The Problem Following messages are logged when restarting sshd service in a CentOS/RHEL 5/6 system. Dec 14 00:15:19 geeklab sshd[9182]: Received signal 15; terminating. Dec 14 00:15:19 geeklab sshd[9274]: Server listening on :: port 22. Dec 14 00:15:19 geeklab sshd[9274]: error: Bind to port 22 on 0.0.0.0 failed: Address already in use. The Solution When […]

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 […]

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 […]

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 […]

The Problem The system’s account will be expired by policy but need to run to cron job by that account. When expired, cron job was failed by PAM with below message: Jul 10 00:31:01 geeklab crond[2860]: CRON (xxx) ERROR: failed to open PAM security session: Success Jul 10 00:31:01 geeklab crond[2860]: CRON (xxx) ERROR: cannot […]

This post explains the steps to add a network printer on a Linux Server. 1. Verify if new printer already exists # lpstat -p Note: This command will list all installed printers. 2. Verify if printer has a DNS record: # host [printer name] 3. If error found in verifying if printer has a DNS […]

This post explains the steps to remove network printers on a Linux Server. 1. Verify if Printer exists: # lpstat -p 2. Modify /etc/hosts and remove printer details: # vi /etc/hosts 3. Remove printer in the server: # sudo lpadmin -x [printer name] 4. Verify if printer has been successfully removed: # lpstat -p | […]

Question: How can we change the network bonding configuration from one mode to another? Steps to change the network bonding configuration. Temporarily Change the Bonding Mode In this case, this changes the bonding mode in the running system configuration, but not permanently. Step 1: Check the current mode set: # cat /sys/class/net/bond0/bonding/mode Step 2: Bring […]