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 same file. How to know when a file has ACL attached to it ls -l command would produce a output as show below. Note the + sign at the end of the permissions. This confirms that the … [Read more...] about RHEL 7 – RHCSA Notes – Create and manage Access Control Lists (ACLs)
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 for oracle Enter the new value, or press ENTER for the default Minimum Password Age : Maximum Password Age : Last Password … [Read more...] about RHEL 7 – RHCSA Notes : Change passwords and adjust password aging for local user accounts
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 users in the group. But you can not remove the primary group of an existing user. You must remove the user before removing the group. # groupdel group_name - Use the gpasswd command to … [Read more...] about RHEL 7 – RHCSA Notes : Create, delete, and modify local groups and group memberships.
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 user shell for new user to /bin/ksh : # useradd -D -s /bin/ksh Examples To simple add a user with all default options : # … [Read more...] about RHEL 7 – RHCSA Notes : Create, delete, and modify local user accounts
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: # date Mon Sep 12 19:41:40 IST 2016 The date command provides a variety of output formatting options. You can also time and date in future or past. Few examples are given below. 1. … [Read more...] about RHEL 7 – RHCSA Notes : Configure a system to use time services
Previous versions of Oracle Linux use init scripts located in the /etc/rc.d/init directory to start and stop services. In RHEL 7, these init scripts have been replaced with systemd service units. Service units have a .service extension. Use the systemctl command to list all loaded service units: # systemctl list-units --type service --all UNIT LOAD ACTIVE SUB DESCRIPTION auditd.service loaded active running Security … [Read more...] about CentOS / RHEL 7 : Beginners guide to systemd service units
In some cases you may want to extract the initramfs image file to check built-in contents. This post provides steps to extract initramfs image files for RHEL 7. Unlike previous version, on RHEL 7 using cpio command for the initramfs image file will not extract all files (or will give some error). For example: # ls -la /boot/initramfs-$(uname -r).img -rw------- 1 root root 19602671 Feb 4 2016 /boot/initramfs-3.10.0-229.el7.x86_64.img # file … [Read more...] about CentOS / RHEL 7 : How to extract initramfs image and edit/view it
For the new installation of RHEL 7, GUI doesn't come with the default installation. If you do not click on the "Software Selection" link and pick "server with GUI" then there will be no GUI after reboot, only "Base Environment " will be installed. To enable GUI after system installation, you can use the following method. Installing the environment group "Server with GUI" 1. Check the available environment groups : # yum grouplist Loaded plugins: langpacks, product-id, … [Read more...] about CentOS / RHEL 7 : How to Install GUI
There are various ways you can configure an IP address in RHEL 7. The posts discusses the use of network interface configuration files to configure the IP address. Each physical network device has an associated network interface configuration file. Network interface configuration files are located in the /etc/sysconfig/network-scripts directory. 1. Use the ip addr command to display your available network interfaces. # ip addr 1: lo: [LOOPBACK,UP,LOWER_UP] mtu 65536 qdisc noqueue state … [Read more...] about CentOS / RHEL 7 : Configuring static IP adress using network interface configuration files
RHEL 7 – RHCSA Notes (Cheat Sheets) Soft links As shown in the diagram soft links or symbolic links simply points to another file. It only contains the pathname of the file to which it is pointing 1. Creation method # touch file # ln -s file link # ls -l -rw-r--r-- 1 root root 0 Sep 19 14:41 link lrwxrwxrwx 1 root root 5 Sep 19 15:41 link -> file The "l" in the "ls -l" command output above indicates that the file is a soft link. 2. The size of the soft … [Read more...] about RHEL 7 – RHCSA Notes : Create hard and soft links.