The GRUB2 configuration file /boot/grub2/grub.cfg – Starting RHEL 7 GRUB 2 is the bootloader. The GRUB 2 configuration file is /boot/grub2/grub.cfg. – Do not edit this file directly. Use the grub2-mkconfig command to generate grub.cfg. This command uses the template scripts in /etc/grub.d and menu-configuration settings taken from /etc/default/grub when generating grub.cfg. – The /etc/grub2.cfg […]
Archives for September 2017
CentOS / RHEL 7 : How to reinstall GRUB2 from rescue mode
CentOS / RHEL 7 now includes GRUB2 which uses a new way of installing to the MBR of your boot device. You may have to reinstall the GRUB2 bootloader if your system is not bootable after a failure. In order to reinstall GRUB2 you have to boot into rescue mode. Follow the steps below to […]
CentOS / RHEL 6 : how to start the services interactively during boot (to disable/abort some services)
There is an option with RHEL / CentOS 6 to start the services interactively during system boot up. We can use it to troubleshoot any booting issues related to services. By default, this feature is not available and you need to enable it using either of the 2 methods described below. Method 1 – Using […]
Installing CentOS / RHEL 7 (step by step with screen shots)
The posts provide a step by step installation procedure for CentOS / RHEL 7. We have used CentOS 7.3 image for the purpose of this post. Anaconda Is the installation program used by CentOS / RHEL and other Linux distributions Runs in textual or graphical mode Supports installation from local or remote sources – CD, […]
UNIX / Linux : How to lock or disable an user account
There are several ways in which user account can be locked or disabled. The posts discusses few of the most widely used ways. 1. Lock the password To lock a users account use the command usermod -L or passwd -l. Both the commands adds an exclamation mark (“!”) in the second field of the file […]
UNIX / Linux : how to force user to change their password on next login after password has reset
The Ask How to require a user to change their password the next time they login? User must be force to change the password for the first time only after the password has been reset. 1. Using chage command This can be done using the chage command with -d option. As per man page of […]
crontab error : “You (user) are not allowed to access to (crontab) because of pam configuration.”
Issue crontab -l command fails with the following error. # crontab -l You (user) are not allowed to access to (crontab) because of pam configuration. You would see below logs in the cron log file /var/log/cron: Sep 19 11:01:01 geeklab crond[125479]: (user) PAM ERROR (Permission denied) Sep 19 11:01:01 geeklab crond[125479]: (user) FAILED to authorize […]
CentOS / RHEL : How to mount filesystems using UUID
The device can be identified by a full path to a block device (for example, /dev/sda3) , a universally unique identifier (UUID; for example, UUID=3bf2d836-be7d-4e69-a1ff-4ffd2661edcf) , or a volume label (for example, LABEL=home). 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 […]
How to install CentOS / RHEL 7 on RAID Partition
The post discusses the installation procedure of CentOS / RHEL 7 on RAID 1 partition. We will use 2 disks for the installation so as to get the RAID 1 configuration. We will use Below settings for root, swap and /boot partitions : Device Type – RAID RAID level – RAID 1 File system – […]
CentOS / RHEL : How to create and host yum repository over httpd
YUM (Yellowdog Updater, Modified) provide more services and functionality than is available with the rpm command and other RPM-based tools. With Yum tools and plug-ins, you can: List software packages, both installed and available, in local or remote repositories Check for package dependencies (packages required to install a package) Create new repositories and enable or […]