Home > Articles > Security > Network Security

Managing Users and Security in openSUSE Linux

  • Print
  • + Share This
Michael McCallister shows how to sett up user accounts and create and manage groups that work together — particularly useful in multiuser office settings, but also important for individual users.
This chapter is from the book

This chapter is from the book

IN THIS CHAPTER

  • User Accounts and Permissions
  • Who Needs What? Managing Groups
  • Passwords: The First Line of Security
  • Monitoring User Activity
  • Letting Mortals Play at Wizardry: SuperUsers
  • References

The heart of Linux security is determining who can use what file and what kind of use is permitted. This is not all there is to making Linux a more secure system, but ultimately, what is the purpose of computer security? Keeping the bad guys out of your files.

In this chapter, you will learn about setting up user accounts and creating and managing groups that work together. There are decisions to make about user passwords: Does the user select them, or does the administrator? How strong must passwords be? How often to change them? In this chapter, you'll get advice about security. In short, you'll learn about the human side of system administration.

This stuff is particularly important for system administrators in a multiuser office setting, but even if you are working by yourself, you will need to become familiar with permissions and passwords. This is the area where trouble often starts, and it's the first thing to check when you can't run something.

User Accounts and Permissions

All Linux systems require one administrator, the Root, and at least one generic user, who can be the same person. The Root is, as noted often here, all powerful. Generic users can be restricted to the point of being able to read only a single file, or have full run of the system as the SuperUser (su). This section will help you better understand how the permissions system works, beyond what you learned in Chapter 5, "Getting Started with openSUSE."

Setting Up User Accounts in YaST

The first user account is set up during the openSUSE installation. Adding users is a simple task in YaST.

In YaST, go to Security and Users, then User Management. YaST will review the current user accounts and display them in the first screen (see Figure 19.1).

Figure 19.1

Figure 19.1 The YaST User and Group Administration tool.

Besides the standard operations of Adding and Deleting users, you can perform several user-related tasks from this screen:

  • Change passwords and access rights for existing users
  • Allow some users to log in without a password
  • View and edit system users (more about this in the next section)
  • Set default permissions and groups for new users
  • Set password encryption standards
  • Configure user-related information for Lightweight Directory Access Protocol (LDAP), Samba, Network Information Service (NIS), and Kerberos services

You will explore some of these options later, but for now you'll create a new user. In this example, you're going to create a user called drone77. Click Add. Figure 19.2 will appear.

Figure 19.2

Figure 19.2 Set username and password in the first Add a New Local User screen.

YaST asks for the user's full name. This is not required, but YaST will use this information to provide a suggestion for the system username. Because we already have a username picked out, enter drone77 on the User Login line. Type an initial password for this user. The Help pane on the left offers some pointers. The password must be between 5 and 72 characters; it is case sensitive (so mix in some capital letters) and can include spaces and just about any character on the keyboard.

To give drone77 a chance to select his own password, you need to set the expiration date. Click the Password Settings tab and Figure 19.3 opens.

Figure 19.3

Figure 19.3 Let the user set a password on first login with these settings.

The default settings are for a system in which passwords are set once and never changed. This is OK for a single-user system with a modem connection to the Internet, but it's a bad idea if you have an always-on connection, such as a DSL or cable-modem connection.

Frequent changes of your users' passwords is another way of staying one step ahead of the attackers. A good rule is to reset passwords every 3–6 months. drone77 is set to change passwords every 90 days.

To let drone77 choose a password on login, you must set the Expiration Date for today (in the YYYY-MM-DD format) and set the Days After Password Expires with Usable Login to 1 or 0. The Days Before Password Expiration to Issue Warning can stay at the default, but can be adjusted to your preference. The system will then prompt drone77 to change passwords. When that happens, you should return here to delete the Expiration Date.

Click the Details tab to review the other defaults associated with this user. These default settings are generally OK, but there may be items to adjust. In this dialog box, you can set the following:

  • User ID (UID)—Every user must have an ID number. Generic users must have UIDs greater than 499; YaST starts at UID 1000 to be safe. You can change this if you want, but do this only when you create the account. Ownership rights are associated with UID numbers, so changing the number will orphan any files outside of the user's home directory.
  • Home Directory—By default, this is /home/<username>, but you can change this here. The best reason to change the home directory is if this user is really just a "persona" of another user (like you, for example), who wants to have a single /home directory to store data in.
  • Home Directory Permission Mode—By default, permissions for files in the /home directory are set at 755 (rwxr-xr-x). If you would like other system users to have Write permission, change this to 775.
  • Additional User Information—This line is for finger information. For privacy's sake, leave this blank (see "Changing User Information" in Chapter 5).
  • Login Shell—This is the default shell for this user. By default, it's bash. Use the drop-down menu, which has the path to every installed shell on the system, to change shells.
  • Default Group and Additional Group Membership—By default, YaST assigns users to the Users group and also to the Dialout and Video groups. You'll learn more about assigning groups in the next section.

When you're through adjusting these settings, click Accept to add this user to your system. drone77 should now appear on the list of Local Users. Click Finish to return to YaST.

System Users

Some applications need to own their files and processes to function securely. This is accomplished by creating system users. These are usually the daemons that always run in the background (man, lp/print, mail, news, and bin), but also include a few other applications, such as MySQL and the Games user. System users do not log in or have home directories, but they have passwords. They also have control over files that other generic users do not have. System users belong to their own group; that is, bin belongs to the Bin group.

View the list of system users in the User Administration screen by clicking Set Filter and selecting System Users. You should never have to configure these yourself, even as Root.

RWX: Understanding Permissions

Most of the practicalities of setting permissions were covered in Chapter 5. The focus there is on the hows of permissions. It's just a question of assigning Read, Write, and eXecute permissions to the Owner, Group, and World groups. You can do this either from the shell, using the chmod command, or in a GUI file manager. From the shell you can use octals or letter switches.

In this section, the focus is on why you want to set permissions in a particular way. Consider that permissions are the heart of security, as previously mentioned, and start with trying to think like a black hat—a would-be attacker. How can you use these three switches—RWX—to your advantage?

  • Read—The safest permission to grant is Read. Giving Read access to a file allows viewing the contents of a file. Read access to a directory allows access to the list of files in that directory. In most cases, someone viewing a file (with bad intent or not) is harmless. But what if it's a critical document that needs to be kept from prying eyes? You probably want to encrypt the file as well, but removing the Read option is another step. What if an attacker wants to see if a file known to have a security hole is on your system? An attacker (or a software bot) can do that with World Read access to that directory.
  • Write—Giving Write access to a file allows someone to change the content of a file. Write access to a directory means permitting renaming or deletion of existing files and creation of new files in that directory. It's a little easier to see the danger. Give World Write access to your web-server directory, and your site is a prime candidate for defacement. Give an attacker Write access to your. login file (even without Read access), and someday you won't be able to login because that filename will have been changed. These types of things probably don't happen often, but they are the kinds of mistakes that happen frequently enough to be troublesome.
  • Execute—Theoretically, any file in Linux can be made executable by setting this permission. In practice, executable files are standard programs or files that can be used as scripts. In a directory, execute rights are also called search permissions. It means you can use the directory's name when accessing its files.
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020