Free LPI 101-500 Practice Exam with Questions & Answers | Set: 7

 The command foo 1> bar redirects the standard output (stdout) from the command foo to the file bar, overwriting the existing contents of the file. The number 1 before the redirection operator > indicates the file descriptor of the stdout stream, which is 1 by default. The redirection operator > means that the output of the command is written to the file, replacing any previous data in the file. The file name after the redirection operator is the destination of the output. For example, if the command foo prints “Hello world” to the stdout, and the file bar contains “Goodbye world”, the command foo 1> bar will write “Hello world” to the file bar, erasing “Goodbye world”. The other options are not correct because:

A. The stdout from the command foo is appended to the file bar: This is not what 1> does, because it overwrites the file, not appends to it. To append the output to the file, the operator >> should be used instead of >.

C. The command foo receives its stdin from the file bar: This is not what 1> does, because it redirects the output, not the input. To redirect the input from the file, the operator < should be used instead of >.

D. The command foo receives its stdin from the stdout of the command bar: This is not what 1> does, because it redirects the output to a file, not to another command. To redirect the output to another command, the operator | (pipe) should be used instead of >.

E. The stderr from the command foo is saved to the file bar: This is not what 1> does, because it redirects the stdout, not the stderr. To redirect the stderr, the file descriptor 2 should be used instead of 1.

To save a file and exit the vi/vim editor, you need to switch to command mode by pressing the Esc key, then type a colon (:) followed by a command. There are two commands that can save a file and quit the editor: x and wq. The x command writes the buffer to the file only if there are unsaved changes, while the wq command always writes the buffer to the file and updates the file modification time. Both commands are followed by an exclamation mark (!) to force the operation and override any warnings. Therefore, the correct sequences are:

Esc ZZ: This is equivalent to typing :x and hitting Enter.

Esc :wq!: This writes the buffer to the file and quits the editor, ignoring any warnings.

The other options are incorrect because:

Ctrl :w! is not a valid sequence. The Ctrl key does not switch to command mode, and the w command only saves the file without exiting.

Esc zz is not a valid sequence. The zz command does not exist in vi/vim.

Ctrl XX is not a valid sequence. The Ctrl key does not switch to command mode, and the XX command does not exist in vi/vim.

The -v option for the egrep command activates the invert matching mode, which means that it only outputs the lines that do not match the given pattern or regular expression. This is useful for filtering out unwanted lines or finding exceptions in a file. For example, the following command will output all the lines in the file my_text that do not contain the word “Linux”:

egrep -v Linux my_text

The -v option can be combined with other options to modify the output format or behavior of the egrep command. For example, the -c option will count the number of non-matching lines instead of printing them, and the -i option will ignore the case of the pattern while matching. References:

[LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.7: Perform basic file management, Weight: 4, Key Knowledge Areas: Use of egrep to search for extended regular expressions in text output.

[Linux egrep Command with Examples], Topic: Invert Matching with egrep.

∗∗Thegrepcommandthatwillprintonlythelinesthatdonotendwitha/inthefilefooisgrep−v′/’ foo. This command uses the following options and pattern:

-v: Inverts the matching, meaning that it only outputs the lines that do not match the pattern. /:Matchesa/characterattheendofaline.The symbol represents the end of a line in regular expressions. foo: The name of the file to search.

The output of this command will show all the lines in the file foo that do not have a / as the last character. For example, if the file foo contains the following lines:

/home/user/ /var/log/messages /etc/passwd /usr/bin/

The output of the command will be:

/var/log/messages /etc/passwd

The other commands are incorrect for the following reasons:

grep ‘/$’ foo: This command will print only the lines that do end with a / in the file foo, which is the opposite of what is required.

grep ‘/#’ foo: This command will print only the lines that contain the string /# in the file foo, which is not related to the question.

grep -v ‘/#’ foo: This command will print only the lines that do not contain the string /# in the file foo, which is also not related to the question.

The + symbol in a grep regular expression means to match the preceding character or character set one or more times. In other words, it means to repeat the previous element at least once. For example, the regular expression ^d[aei]\+d$ will match any word that starts and ends with d and has one or more of the letters a, e or i in between. Some examples of words that match this pattern are dead, deed, died, daiid, etc. The other options are either incorrect or not applicable. The * symbol means to match the preceding character or character set zero or more times. The ? symbol means to match the preceding character or character set zero or one times. The \+ symbol means to match a literal + symbol, not a repetition modifier. References:

LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.3 Perform basic file management

LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

The correct permissions and ownership for the file /etc/passwd are:

B. -rw-r–r-- 1 root root 531 Jun 5 22:45 /etc/passwd

The /etc/passwd file is a plain text-based database that contains information for all user accounts on the system. It is owned by root and has 644 permissions. The file can only be modified by root or users with sudo privileges and readable by all system users. The permissions and ownership of the file are important for the security and functionality of the system. The permissions and ownership of the file can be viewed by using the ls -l command. For example:

ls -l /etc/passwd

The output of the command will show the following information:

-rw-r–r-- 1 root root 531 Jun 5 22:45 /etc/passwd

The first column shows the permissions of the file, which are composed of 10 characters. The first character indicates the file type, which is - for regular files. The next nine characters indicate the permissions for the user (owner), the group, and the others, respectively. Each set of three characters indicates the read ®, write (w), and execute (x) permissions. A dash (-) means no permission. In this case, the permissions are:

rw- for the user, which means the user can read and write the file, but not execute it.

r-- for the group, which means the group can only read the file, but not write or execute it.

r-- for the others, which means the others can only read the file, but not write or execute it.

The second and third columns show the owner and the group of the file, which are both root. The root user is the superuser or the administrator of the system, who has full access and control over the system. The root group is the primary group of the root user, which usually has no other members.

The fourth column shows the size of the file in bytes, which is 531 in this case. The fifth and sixth columns show the date and time of the last modification of the file, which are Jun 5 22:45 in this case. The last column shows the name of the file, which is /etc/passwd in this case.

The other options are not correct because:

A. -rw------- 1 root root 531 Jun 5 22:45 /etc/passwd: This option has the wrong permissions for the file. The permissions are 600, which means only the user (root) can read and write the file, and the group and the others have no permissions at all. This would prevent the system users from reading the file, which would cause problems for the login process and other utilities that rely on the file.

C. -rw-r–r-- 1 1 531 Jun 5 22:45 /etc/passwd: This option has the wrong owner and group for the file. The owner and group are both 1, which is the numeric ID of the user and group. However, the numeric ID of the root user and group is 0, not 1. The user and group with the numeric ID of 1 are usually bin, which is a system user and group that own some system binaries and directories. The bin user and group should not own the /etc/passwd file, as this would compromise the security and functionality of the system.

D. -rw------- 1 1 531 Jun 5 22:45 /etc/passwd: This option has both the wrong permissions and the wrong owner and group for the file. The permissions are 600, which means only the user can read and write the file, and the owner and group are both 1, which is the numeric ID of the bin user and group. This would prevent the system users from reading the file, and give the bin user and group full access to the file, which would cause problems for the security and functionality of the system.

 The environment variable LD_LIBRARY_PATH is used to tell the dynamic linker to look in a specific directory for some of a program’s shared libraries. It is a colon-separated list of directories that are searched by the dynamic linker when looking for a shared library to load1. The directories are searched in the order they are mentioned in. For example, if we have a program that depends on a shared library libfoo.so that is located in /home/user/build/lib, we can run the program with:

LD_LIBRARY_PATH=/home/user/build/lib ./program

This will instruct the dynamic linker to search for libfoo.so in /home/user/build/lib before the default directories. The environment variable LD_LIBRARY_PATH can also be appended to an existing value with the += operator, for example:

LD_LIBRARY_PATH+=:/home/user/build/lib

This will add /home/user/build/lib to the end of the LD_LIBRARY_PATH list. The other options are not valid environment variables for the dynamic linker. LD_LOAD_PATH, LD_LIB_PATH, and LD_SHARE_PATH are not recognized by the dynamic linker. LD_RUN_PATH is a linker option that can be used to embed a library search path in the executable at link time, but it is not an environment variable that can be set or modified at run time2. References:

LPI Exam 101 Detailed Objectives, section 1.101.3

ld-linux(8) — Linux manual page

Setting the dynamic linker with an environment variable - narkive

 The command that updates the linker cache of shared libraries is ldconfig. This command creates, updates, and removes the necessary links and cache for the run-time linker, ld.so, to the most recent shared libraries found in the specified directories. To add a new library directory to the cache, you need to edit the /etc/ld.so.conf file and rerun ldconfig. You can use the -p option to print the current cache contents1.

The other commands are either invalid or unrelated to the linker cache. mkcache, soconfig, and mkldconfig are not standard Linux commands. lddconfig is a typo for ldd, which is a command that prints the shared libraries required by a program2.

The command grub-install is used to install GRUB on a device or a partition. The option --root-directory specifies the directory where GRUB images are put. The default is /boot/grub. The argument /dev/sda specifies the device where GRUB is installed, usually the Master Boot Record (MBR) of the disk. Therefore, the command grub-install --root-directory=/custom-grub /dev/sda will install GRUB on the MBR of /dev/sda and put the GRUB images under the directory /custom-grub/boot/grub. This means that the new configuration files, such as grub.cfg, will be found in the directory /custom-grub/boot/grub. References:

GNU GRUB Manual 2.06: Installing GRUB using grub-install

Installing GRUB using grub-install - GNU GRUB Manual 0.97

 The main configuration file for GNU GRUB is grub.cfg, which is usually located in /boot/grub/ or /boot/grub2/ depending on the distribution. This file contains the menu entries for the boot loader, each with a title, a kernel image, an initrd image, and optional parameters. The grub.cfg file is not meant to be edited manually, as it is generated by the grub-mkconfig command, which reads the settings from /etc/default/grub and the scripts in /etc/grub.d/. The /etc/default/grub file contains the global options for GRUB, such as the default menu entry, the timeout, the theme, etc. The /etc/grub.d/ directory contains executable scripts that are run by grub-mkconfig to generate the menu entries for each operating system or kernel found on the system. For example, the script 10_linux generates the entries for the Linux kernels installed by the package manager, while the script 30_os-prober generates the entries for other operating systems detected on the system, such as Windows. To make changes to the GRUB configuration, one should edit the /etc/default/grub file and/or the scripts in /etc/grub.d/, and then run grub-mkconfig -o /boot/grub/grub.cfg to update the grub.cfg file. References:

2, 102.2 Install a boot manager

4, 102.2 Install a boot manager

man grub-mkconfig