RHEL 7 – RHCSA Notes (Cheat Sheets) SELinux modes SELinux gives that extra layer of security to the resources in the system. It provides the MAC (mandatory access control) as contrary to the DAC (Discretionary access control). Before we dive into setting the SELinux modes, let us see what are the different SELinux modes of […]
Archives for September 2016
RHEL 7 – RHCSA Notes – Create and manage Access Control Lists (ACLs)
RHEL 7 – RHCSA Notes (Cheat Sheets) The file access control lists (FACLs) or simply ACLs are the list of additional user/groups and their permission to the file. Although the default file permissions does their jobs perfectly, it does not allow you to give permissions to more than one user or one group on the […]
CentOS / RHEL : How to change password hashing algorithm
authconfig The Linux user password hashing algorithm is also configurable. Use the authconfig command to determine the current algorithm being used, or to set it to something different. To determine the current algorithm: # authconfig –test | grep hashing password hashing algorithm is sha512 Change the hashing algorithm To change the algorithm, use the –passalgo […]
RHEL 7 – RHCSA Notes : Change passwords and adjust password aging for local user accounts
RHEL 7 – RHCSA Notes (Cheat Sheets) Password configuration password aging requires users to change their password periodically. Use the chage to configure password expiration. The syntax is : # chage [options] user_name – When you fire the command chage, the currently set options are displayed as well. # chage oracle Changing the aging information […]
CentOS / RHEL : How to assemble a software RAID in Rescue mode
mdadm (multiple devices admin) is an extremely useful tool for running RAID systems. It’s is a tool for creating, managing, and monitoring RAID devices using the md driver. It can be used as a replacement for the raidtools, or as a supplement. The pos describes a way to assemble a software RAID in rescue mode. […]
RHEL 7 – RHCSA Notes : Create, delete, and modify local groups and group memberships.
RHEL 7 – RHCSA Notes (Cheat Sheets) Group administration – Use the groupadd command to add a new group : # groupadd [options] group_name – Use the groupmod command to modify an existing group : # groupmod [options] group_name – Use groupdel to delete the group. You can remove a group even if there are […]
RHEL 7 – RHCSA Notes : Create, delete, and modify local user accounts
RHEL 7 – RHCSA Notes (Cheat Sheets) Adding a user account Use the useradd command to add new user : # useradd [options] [username] The default settings for new user can viewed and modified using the -D option : # useradd -D GROUP=100 HOME=/home INACTIVE=-1 EXPIRE= SHELL=/bin/bash SKEL=/etc/skel CREATE_MAIL_SPOOL=yes For example, to change the default […]
RHEL 7 – RHCSA Notes : Configure a system to use time services
RHEL 7 – RHCSA Notes (Cheat Sheets) RHEL 7 has 3 command-line utilities to configure the system date and time: 1. date 2. hwclock 3. timedatectl date command Use the date command to display or set the system date and time. Run the date command with no arguments to display the current date and time: […]
CentOS / RHEL : How To Shrink LVM Root File System
During system installation, one may allocate an over-generous amount of disk space to the root partition and may later wish to reclaim any unused space. The post describes how to reduce the space allocated to an root file system on a Linux Volume Manager (LVM) logical volume. Note : this procedure applies only if the […]
CentOS / RHEL : How to migrate storage (LVM) with pvmove Command
Solution: Existing Configuration : Existing Physical Volume: 1.5 TB, /dev/mapper/mpathX Existing Volume Group: data_vg Existing Logical Volume: lv_data01 (/dev/mapper/data_vg-lv_data01) We need to move to the following configuration : Physical Volume: 1.5TB, /dev/mapper/mpathY Volume Group: data_vg Logical Volume: data (/dev/mapper/data_vg-lv_data01) Note: Please take complete backup before performing the storage migration Steps 1. Begin by pvcreate’ing the […]