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Chapter 6 . Study Guide 273 16. D. Permissions on files and directories is changed using the chmodcommand. The chown command is used to change ownership while the chgrpcommand changes the group assigned to the files or directories. The chpermcommand is invalid. See the User and group permissions section for more information. 17. A. The sticky bit value is (1) while the SUID value is 4 and SGID value is 2. See the SUID and SGID and Sticky bit sections for more information. 18. tar czf ang_home.tar.gz /home/angie. The tar command is used with the c option to create a new archive and the zoption specifies that the archive is compressed using the gzip utility. The f option specifies that the archive should be created as the specified file. Utilizing the absolute path ensures that all data within that directory is included in the archive. See the tar section for more information. 19. B. Quotas for specific users are viewed with the quotacommand. The repquota command will provide a report of quota usage for all users. The edquota command is used to edit quotas, and quotaonis used to enable quotas on the system. See the Managing quotas section for more information. 20. C. File systems utilizing quotas are configured in the /etc/fstab file. See the quotaon and quotaoff section for more information. Scenarios 1. which ls The which command uses the ls command as an argument. It locates the ls command that would run at the command line and displays the full path to that command. This allows you to verify that the command being executed is in the correct location. 2. /bin/ls If the results from the first scenario aren t what you expect, then you can specify the absolute path to the lscommand. This ensures that only the ls command at the specified location, in this case the /bin directory, is executed.
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272 Chapter 6 . Study Guide Assessment Questions 1. D. The absolute path to the ls command is /bin/ls. See section Managing Files for more information. 2. ls a*. The wildcard is utilized to specify any character or set of characters, including none. This command would list files and directories with the name of simply aas well as all files and directories that begin with the letter a. See the section Listing directory contents for more information. 3. B. Files can be created using the touch command if the filename specified doesn t already exist. If the file exists then the access time is simply changed. See the section Changing file time stamp for more information. 4. C. Files are renamed and moved using the mvcommand. See the section Moving files for more information. 5. dd. The dd, or direct dump, command is used to convert and copy files. See the dd section for more information. 6. C. The system kernel is stored in the /boot directory. See the System directories section for more information. 7. A. The system configuration files are located in the /etc directory. See the Standard file locations section for more information. 8. B. The root user s home directory is the /root directory. See the System directories section for more information. 9. B. Mail files are found in the /var/spool directory. See the Standard file locations section for more information. 10. D. The slocatedatabase is updated using the updatedbcommand. See the locate section for more information. 11. which. The whichcommand displays the path to the specified command. See the which section for more information. 12. hard link. By default, the ln command creates a hard link to the specified file. See the Hard links section for more information. 13. D. When a soft link is copied, a new copy of the original file is stored at the target location. See the Symbolic links section for more information. 14. A. The permission 7 presents the owner of the file with read (4), write (2), and execute (1) permissions. The group and other permissions here are read (4) and execute (1) for a total of 5. See the Symbolic and numeric permissions section for more information. 15. B. The umask used to create default permissions of 755 is 022. The umask is used to filter permissions from those that are assigned to new files by default. This causes the umaskto be the inverse of the permissions assigned to the files. In this case, the umask filters the write permissions from the group and other permissions. See the umask section for more information.
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Chapter 6 . Study Guide 271 19. Which command is used to view quota information for a specific user? A. edquota B. quota C. repquota D. quotaon 20. File systems utilizing quotas are configured in which file? A. /etc/services B. /etc/hosts C. /etc/fstab D. /etc/mtab Scenarios 1. When running the lscommand you begin having trouble because the wrong command is being executed. What can you do to verify the path to the command is what you expected? 2. In the above example, what command can you type to ensure that the proper ls command is being run? Answers to Chapter Questions Chapter Pre-Test 1. The locate command utilizes the slocate database to find files. 2. The system kernel is located in the /boot directory. 3. The umask sets the default permissions for newly created files. 4. Soft links are allowed to span across file systems. 5. Quotas are enabled using the quotaon command. 6. The ls command is used to list files in a directory. 7. The mkdir command is used to create a directory. 8. The touch command can be used to create an empty file. 9. The whereis command is used to search the PATH statement for a command. 10. The findcommand recursively searches the directory for a specified filename.
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270 Chapter 6 . Study Guide 13. Which of the following results when a soft link is copied? A. A new copy of the soft link is created. B. A hard link to the original file is created. C. A hard link to the soft link is created. D. A new copy of the original file is created. 14. Which of the following represents read, write, and execute permissions for owner and read and execute for all others? A. 755 B. 022 C. 733 D. 557 15. Which umaskwould create the default file permissions of read, write, and execute permissions for owner and read and execute for all others? A. 755 B. 022 C. 220 D. 002 16. Which command is used to change permissions of a file? A. chown B. chperm C. chgrp D. chmod 17. Which value is used to represent the sticky bit? A. 1 B. 2 C. 3 D. 4 18. Which command (with options) is used to create a new archive file named ang_home.tar.gz that is compressed containing the /home/angiedirectory contents?
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Chapter 6 . Study Guide 269 5. The ____________ command is used to copy files while converting them. 6. Which directory contains the system kernel? A. /etc B. / C. /boot D. /proc 7. Which directory contains the system configuration files? A. /etc B. / C. /boot D. /proc 8. Which directory contains the root user s home directory? A. /home B. /root C. /sbin D. /usr 9. Which directory contains the mail files? A. /proc/mail B. /var/spool C. /var/mail D. /usr/mail 10. Which utility is used to update the slocate database? A. locate B. find C. whereis D. updatedb 11. The __________ command is used to display the path to a specified command. 12. The default action of the ln command is to create a _______________.
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268 Chapter 6 . Study Guide STUDY GUIDE The following questions and exercises will allow you to review the information covered in this chapter. Take your time when completing this section of the chapter, carefully reviewing any questions that you may have. Simply answering the question correctly is not as important as understanding the answer, so review any material that you might still be unsure of. Being comfortable with the questions and answers presented here will help you be more prepared for the certification exam questions. Assessment Questions 1. Which of the following shows the use of an absolute path? A. ls B. ls al C. ls /home/angie D. /bin/ls 2. The____________ command will display the contents of the current directory beginning with the letter a. 3. Which of the following commands will create a new file with the name ourgroup? A. file ourgroup B. touch ourgroup C. ls ourgroup D. mkfile ourgroup 4. Which command is used to rename the ourgroup file to mygroup? A. rn ourgroup mygroup B. rn mygroup ourgroup C. mv ourgroup mygroup D. mv mygroup ourgroup
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Chapter 6 . Managing Files 267 . The /var/log directory contains log files while /var/spoolcontains mail and printing files. . The /bin directory holds binaries used during setup, and /sbinhas binaries used by the root user. . The / directory is the root directory, and it contains all other directories. The /root directory is the home directory for the root user. The /homedirectory contains the users home directories. /boot stores the kernel and other files used by the boot loader. The /dev directory stores the devices used on the system, and the /procdirectory is a virtual directory containing system information. . The find utility is used to locate files matching the specified criteria. . The locate utility uses the slocatedatabase to index and search for files on the system. This database is updated using the updatedbcommand. . The which utility is used to display the path of a specified command. . The whereis command searches specific locations for the specified file and manual page entries. . Links function as pointers to files. Hard links cannot span file systems, and changes to a soft link occur in all links to that file. . Permissions are granted to users and group accounts using numeric and letter values. . The chown command is used to change ownership of files and directories while the chgrpcommand is used to change the group assignment of files and directories. . The chmod command is used to change permissions on files and directories. . The umask is used to set the default permissions for newly created files. . The SUID and SGID permissions allow files to be executed using a different user or group account. . The sticky bit is used to allow only an owner to delete files and directories while allowing other users to write to them. . The tar utility allows files to be archived as a single file and for this file to be compressed or uncompressed in one step. . The gzip, gunzip, compress, and bzip2 utilities are used to compress and uncompress files. . Quotas are viewed with quota and repquota. They are enabled with quotaon, disabled with quotaoff, and edited using edquota. …
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266 Part II . Getting Around in Linux Table 6-24 Options Used with quotaon and quotaoff Option Use with quotaon Use with quotaoff -a Enables quotas for all file systems in /etc/fstab that are configured with read/write quotas. Disables quotas for all file systems listed in /etc/fstab. -v Displays a message for each file system with quotas enabled. Displays a message for each file system affected. -u Enables user quotas; this is the default action. Disables user quotas; this is the default action. -g Enables group quotas. Disables group quotas. Key Point Summary File management is an important part of working with any system. Linux provides a variety of powerful tools that make this task easier and allow greater control over files. These tools are extremely important to understand for daily work with Linux systems and essential for the exams. Be sure that you are familiar with all points in the summary presented here before scheduling your exams. . Directory changing is done with the cd command. . Directory contents are displayed using ls. . The file command is useful for examining files to determine file type. . The touch command is used to create files and change time stamps on existing files. . Files are copied with cp and moved or renamed with mv. . The dd command is useful for copying and converting files simultaneously. . The rm command is used to delete files. . The mkdir command creates new directories. . The /etc directory contains configuration files; the /etc/skel directory contains files copied to each user s home directory. . The /usr directory contains /usr/binwith binaries executed by users, /usr/sbin with binaries executed by root user, /usr/local with applications that aren t part of the Linux operating system, /usr/local/bin with third-party software used by users, and /usr/local/sbin with software used by the root user that is installed after the initial operating system installation.
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Chapter 6 . Managing Files 265 Option Use -p user Duplicates the quotas of the user specified for each user specified. -t Used to edit the grace period used for soft limits for each file system. repquota The repquota utility displays a summary of the disk usage and quotas for the specified file systems. The current number of files and amount of space (in kilobytes) for each user is displayed, along with any quotas created using edquota. Users on the system can use this utility for viewing quota information for their account; the superuser can view quota information for all users. Table 6-23 covers the options used with repquota. Table 6-23 Options Used with repquota Option Use -v Displays information for all quotas, even if there is no usage. -g Displays quota information for groups. -u Displays quota information for users. This is the default. -a Displays information on all file systems indicated in /etc/fstab with quotas. Following is an example of output produced by the repquota command: # repquota v / *** Report for user quotas on / (/) Block limits File limits User used soft hard grace used soft hard grace root 8 0 0 1 0 0 quotaon and quotaoff The quotaon and quotaoffutilities are used to enable and disable file system quotas. The quota.userand quota.group files must exist before you can run the quotaon utility. Several options are available for use with both commands. The use of the option varies somewhat depending on whether the option is used with quotaon or quotaoff. The options and uses for both commands are shown in Table 6-24.
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264 Part II . Getting Around in Linux its quota limit, the user will be unable to create new files, regardless of the user s account quota. This is important to remember when defining quotas. An example of the correct use of the quota utility is the following: # quota angie Disk quotas for user angie (uid 501): none The quota utility has several options to specify which information is displayed. These options are covered in Table 6-21. Table 6-21 Options Used with quota Option Use -u Displays user quota information. This is the default action. -v Displays quotas on file systems with no storage allocated. -q Displays information for file systems with usage exceeding the quota. -g Displays group quota information. edquota The edquota utility is used by the superuser to edit user and group quotas. The superuser uses this utility to set three different quota limits. The soft limit is a limit that can be exceeded for a period of time. The grace period is the period of time in which a user can exceed their soft limit. The hard limit is a limit at which a user can no longer create new files. The correct use of the edquotautility is shown below. In this example angieis given the same quota information as the jason account. # edquota p jason u angie The vi editor is the default editor used with the edquota utility. This utility writes the changes to the quota.user and quota.groupfiles. You can use several options for editing quotas. These options are explained in Table 6-22. Table 6-22 Options Used with edquota Option Use -u Specifies to edit the user quota. This is the default action. -g Specifies to edit the group quota.
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