Chapter 8

1. Chapter 8 Basic Administration Tasks Guide to Linux Installation and Administration, 2e

2. Objectives In this chapter, you will: • Create and manage Linux user accounts • Install and maintain types of Linux systems • Manage processes on Linux using basic commands Guide to Linux Installation and Administration, 2e

3. Managing User Accounts • To complete any operation in Linux, a person must first log in using a valid user account name and password • Setting up and maintaining these user accounts is an important part of the work of a system administrator Guide to Linux Installation and Administration, 2e

4. Types of User Accounts • Types of user accounts include: • root account • Regular accounts • Special accounts Guide to Linux Installation and Administration, 2e

5. The root Account • The administrative account (the superuser) on a Linux system is named root • The root user can perform any operation on a Linux system • The su utility (for substitute user) temporarily changes your access rights to those of another user Guide to Linux Installation and Administration, 2e

6. Regular Users • Regular user accounts are for users who log in at a keyboard and use the Linux system • Regular user account names typically use a combination of first name or initial and last name or initial Guide to Linux Installation and Administration, 2e

7. Special Users • Special accounts cannot be used to log in • Special accounts are used by programs running on Linux Guide to Linux Installation and Administration, 2e

8. Linux Groups • A group is a collection of user accounts that can be collectively granted access to files and directories • A user can be a member of multiple groups, but can only have one primary group • A User Private Group system creates a group with a single member for each new user account Guide to Linux Installation and Administration, 2e

9. A User as a Member of Multiple Groups Guide to Linux Installation and Administration, 2e

10. User and Group Files • User account information is stored in the file /etc/passwd • To edit the /etc/passwd file, use the special editing program vipw • Groups on a Linux system are defined in /etc/group • To edit the /etc/group file, use the command vigr Guide to Linux Installation and Administration, 2e

11. Shadow Passwords • Encrypted passwords are stored in /etc/shadow • Regular users cannot read encrypted passwords • Shadow Password Suite is a collection of password-related programs that have been modified to recognize the /etc/shadow file Guide to Linux Installation and Administration, 2e

12. Creating New User Accounts • New user accounts can be created • With the useradd command • With various graphical utilities • Default settings apply when using the useradd command alone • Default settings can be modified on the command line or by editing a configuration file for useradd Guide to Linux Installation and Administration, 2e

13. Configuring Users Graphically in Red Hat Linux 7.3 Guide to Linux Installation and Administration, 2e

14. useradd Command Options Guide to Linux Installation and Administration, 2e

15. Changing User Passwords • A password is not defined by useradd when a new user account is created • The passwd command is used to define or change a user’s password • You must enter the new password twice Guide to Linux Installation and Administration, 2e

16. Creating New Groups • To create a new group, use the groupadd command • To add a new group, include the group name as a parameter Guide to Linux Installation and Administration, 2e

17. Modifying User and Group Accounts • The usermod command allows you to modify user account parameters stored in /etc/passwd or /etc/shadow • The groupmod command lets you modify membership of a group Guide to Linux Installation and Administration, 2e

18. Automating Home Directory Creation • Files contained in /etc/skel are automatically copied into each user’s home directory at the time you create the account • You should place files in /etc/skel when you first install Linux Guide to Linux Installation and Administration, 2e

19. Disabling User Accounts • You can temporarily or permanently disable a user account • Accounts can be deleted using the userdel command • To temporarily disable a user’s account, change the password with the passwd command Guide to Linux Installation and Administration, 2e

20. Maintaining File Systems • File system refers to an organized set of data that can be accessed via the standard Linux directory structure • To access a file system in Linux, it must first be mounted into the root directory structure • A mount point is the path in the directory structure where you access the data in a file system • Use the mount command to make a new file system accessible via a mount point Guide to Linux Installation and Administration, 2e

21. Automatically Mounted File Systems Guide to Linux Installation and Administration, 2e

22. File Systems Mounted in a Linux Directory Structure Guide to Linux Installation and Administration, 2e

23. Checking File System Status • The df command displays space usage information for each file system that is currently mounted • The du utility lists the size of a directory and all its subdirectories • You can use various graphical tools and system administration scripts to check the status of file systems Guide to Linux Installation and Administration, 2e

24. Creating New File Systems • You can install new file systems that are permanent or temporary • File systems can be stored on a device with removable media or fixed media • Once the hard disk or other device is installed, you can use the Linux fdisk command to examine its partitions, creating new Linux partitions Guide to Linux Installation and Administration, 2e

25. Using the fdisk Utility • To manage partitions in Linux after the operating system is installed, use the fdisk utility • The fdisk utility can configure partition data on a hard disk • Your modifications to the partition table are only effective when you write the changes to disk with the w command to exit fdisk Guide to Linux Installation and Administration, 2e

26. fdisk Commands Guide to Linux Installation and Administration, 2e

27. Sample Output of the p Command in fdisk Guide to Linux Installation and Administration, 2e

28. Formatting File Systems • File system journaling is a feature that protects against data corruption by tracking each “write” to the hard disk in a special way so that it will either be completely finished or left completely undone • New partitions must be formatted using mke2fs or mkswap before they can be used Guide to Linux Installation and Administration, 2e

29. Mounting File Systems • After you have formatted a file system, you can mount it • To access a file system, you use the mount command • The floppy disk drive and CD-ROM drive are mounted to /mnt/floppy and /mnt/cdrom Guide to Linux Installation and Administration, 2e

30. Unmounting File Systems • To unmount a file system, use the umount command with the device name or mount point • A file system cannot be in use when you unmount it Guide to Linux Installation and Administration, 2e

31. Automating File System Mounting • The new file systems that you create from additional hard disks or other devices can also be automatically mounted at boot time • The key to automounting file systems is the /etc/fstab configuration file which contains one line for each file system that you want to have automounted when Linux boots Guide to Linux Installation and Administration, 2e

32. Option Field Settings for the mount Command Guide to Linux Installation and Administration, 2e

33. Managing Swap Space • The swap space is a special partition type used by the Linux kernel for virtual memory • You can use the mkswap command to format a swap partition • Swap space is activated by the swapon command within the system initialization scripts • The vmstat command displays current status details for how virtual memory is being used Guide to Linux Installation and Administration, 2e

34. Setting Quotas on Disk Usage • Limits on the amount of hard disk space that any user or group can use are called disk quotas • Use the edquota command to establish a quota for one or more users or groups • Activate the quota system using the quotaon command Guide to Linux Installation and Administration, 2e

35. Simple Task Management • To control processes running on Linux, you can use the following: • The ps command • The bg command • The fg command Guide to Linux Installation and Administration, 2e

36. Job Control in the Shell • When you start a program, that program takes control of the command line where you are working • The jobs command lists all jobs or processes that are running from the current shell • The fg command places processes in the foreground • The bg command places processes in the background command Guide to Linux Installation and Administration, 2e

37. Using Virtual Consoles • A virtual console is a separate login screen that you access by pressing a combination of keys on your keyboard • A virtual console allows you to start multiple text-based login sessions on the same computer • The virtual consoles are assigned to the function keys Guide to Linux Installation and Administration, 2e

38. Learning about Processes • A simple ps command shows you only the commands that you have started in the current command-line environment • Multiple processes can be started from a single shell Guide to Linux Installation and Administration, 2e

39. Controlling Processes • The kill command is used to kill, or end, processes • Signals are messages that can be sent between processes • The killall command sends a signal to all processes started by a given command Guide to Linux Installation and Administration, 2e

40. Summary • Types of user accounts include root, regular accounts, and special accounts • New user accounts can be created with the useradd command or with various graphical utilities • New groups can be created with the groupadd command • File systems are accessed by using the mount command to specify a device and a mount point • The df and du commands display status and size information about file systems Guide to Linux Installation and Administration, 2e

41. Summary • The fdisk utility can configure partition data on a hard disk. • The vmstat command displays how virtual memory is being used • Within a shell, the jobs command manages these processes, placing them in the foreground or background • Virtual consoles let you log in at multiple independent text-mode screens • The kill command sends signals to processes or to the Linux kernel when necessary to end a process Guide to Linux Installation and Administration, 2e