Interactive shells and login shells

See also switching users using su

Whenever a new user is created, by default, a set of (usually hidden) config files will get copied to the user’s new home folder. These files are actually duplicate of all the files contained in the /etc/skel directory:

$ ls -la /etc/skel/
total 24
drwxr-xr-x.  2 root root   62 Feb  2 13:31 .
drwxr-xr-x. 78 root root 8192 Mar 28 14:09 ..
-rw-r--r--.  1 root root   18 Sep  6  2017 .bash_logout
-rw-r--r--.  1 root root  193 Sep  6  2017 .bash_profile
-rw-r--r--.  1 root root  231 Sep  6  2017 .bashrc

the useradd commands automatically copies all the content from this folder and places it in the user’s home directory.

when a user logs into a RHEL machine (using username and password), the following scripts are executed automatically (in this order):

/etc/profile           # (this sets up user env variables, e.g. path, hostname, histsize….etc)…this script will also trigger:

/etc/profile.d         # (directory containing lots of other files.

{user’s home folder}/.bash_profile # can be used to add your own stuff including overriding what was set in the /etc/profile script.

{user’s home folder}/.bashrc       # (used for setting local variables e.g. the PS1 variables)

However these does get executed when a non-login shell (aka interactive shell) is generated. a interactive shell is a shell that gets opened but without getting a username/password prompt. Here are some ways to start a non-login shell:

–                 Applications=>system tools=>terminal

–              When you start a shell script, linux will automatically create a new shell for that script to run in, and this new shell is a non-login shell.

–                 At the command line, type ksh, followed by bash.

In a non-login shell the following scripts are run:

 

1. {user’s home folder}/bashrc,

2. /etc/bashrc,

3. /etc/profile.d (have a look through these script to familiarize yourself)

Take the RHCSA Quiz

This article is part of our RHCSA Study guide (click on the yellow tab on the far left). By the end of this article you should be able to answer the following questions:


What are three possible commands to start a full login-shell for the user called david?

$ su – david # note: option l is implicitedly assumed here.
# or
$ su -l david
# or
$ ssh david@centos7machine


Which shell scripts gets triggered as part of this command?

– /etc/profile # which in turn calls all scripts inside /etc/profile.d folder, and then it calls:
– ~/.bash_profile # (If for any reason this doesn’t exist, then it will look for ~/.profile) which in turn calls:
– ~/.bashrc # which in turn calls:
– /etc/bashrc


While logged in as the root user, What is the command to start a non-login shell for the user called david?

$ su david
# or:
$ bash

Which shell scripts gets triggered as part of this command?

– ~/.bashrc # which in turn calls:
– /etc/bashrc
Note: all the profile related scripts are ignored. Hence privilege is set but environment variable are unset.

What is the command to view info about the package 'nmap'?

$ yum info nmap


What is the command to install the package 'nmap'?

$ yum install nmap


What are the 3 commands to list all packages, installed packages, and available packages?

$ yum list all
$ yum list installed
$ yum list available

What is the command to install all the latest packages including security updates?

$ yum update

What is the command to install the 'tree' package from a repo recalled 'epel' repo rather than any other repo?

$ yum –enablerepo=epel install tree

What is the command to list all package groups?

$ yum grouplist


What is the command to install a the tree.rpm file which is in the current directory?

$ yum localinstall tree.rpm