101-500 Exam Dumps : LPIC-1 Exam 101, Part 1 of 2, version 5.0

The /proc/ directory is a virtual filesystem that provides a view of the kernel’s data structures and parameters. It contains information about processes, hardware, memory, modules, and other aspects of thesystem. The files in /proc/ are not stored on disk, but are generated on the fly by the kernel when they are accessed. Therefore, any changes to files in /proc/ are immediately recognized by the kernel and affect its behavior. For example, writing a value to /proc/sys/kernel/hostname will change the system’s hostname without rebooting. The files in /proc/ are not all read-only; some of them can be modified by the root user or by processes with the appropriate permissions. The files in /proc/ are readable by any user, unless restricted by the kernel or by the mount options. References: LPI Linux Essentials - 1.101.2, LPI Linux Administrator - 102.3

 The command that lists all currently installed packages when using RPM package management is rpm --query --all. This command displays information about all the packages that are currently installed on the system, including their name, version, release, and architecture1. The output can be customized by using various query options and format specifiers2.

The other commands are either invalid or related to YUM, not RPM. yum --query --all is not a valid YUM command, as YUM does not have a --query option3. yum --list --installed is a valid YUM command, but itlists the packages from the YUM repositories, not the RPM database3. rpm --list --installed is not a valid RPM command, as RPM does not have a --list option2.

References:

• RPM Command in Linux | Linuxize
• rpm(8) - Linux manual page
• Linux package management with YUM and RPM | Enable Sysadmin

The problem with the command

sed -e “s/a/b/” /tmp/file >/tmp/file

is that it tries to read and write from the same file, which results in overwriting the file before the command can process it. The shell sets up the redirection by opening the file /tmp/file for writing and truncating it to zero length. Then it executes the sed command, which tries to read from the same file, but finds it empty. Therefore, the output is also empty and the file remains empty. A possible solution is to use a temporary file for the output and then rename it to the original file name. For example:

sed -e “s/a/b/” /tmp/file >/tmp/file.tmp && mv /tmp/file.tmp /tmp/file

This way, the original file is not overwritten until the sed command finishes successfully. The other options are either incorrect or not applicable. The file order is correct, the sed command does match something in the file, and the > character is valid for redirection. The | character is used for piping, not redirection. References:

• LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.4 Use streams, pipes and redirects
• LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)