Linux Technical Interview QA with Practical Sessions

Explore Linux user administration through practical interview questions and answers, covering creating users with primary and secondary groups, default home directory permissions, and related commands.

Explore linux user administration by examining the /etc/passwd fields, creating users with primary and secondary groups using useradd, and understanding home directory and shell settings, plus login profile differences.

Learn linux user management. Create users with predefined home and shell using useradd -m -d -s -u -g; delete with home via userdel -r; view who, chage -l, and finger.

Learn to grant root-level privileges to a normal user. Add the user to the sudo group and uncomment the group line in sudoers, or enable passwordless sudo.

Learn Linux default file and directory permissions (644 for files, 755 for directories) and how umask 022 shapes them, plus locking and unlocking users with passwd -l and -u.

Explore Linux file permissions and the set UAD concept, showing how a process runs with the owner's rights and enables password updates via the shadow file.

Explain setuid and setgid usage on Linux files and directories, using chmod and numeric modes, and show how these bits control owner and group rights for processes and inheritance.

This lecture shows how the setuid bit on a password-changing binary lets a process inherit read, write, and execute permissions, enabling password changes despite file permissions, and previews sticky bit.

Explore how the sticky bit restricts deletion in directories, ensuring only the owner or root can delete files. Learn how to identify and set this permission and understand folder permissions.

Explain how umask and default file permissions work, show how login.def defines defaults, and cover applying permissions recursively, directory access requirements, and the sticky bit in Linux permission management.

Explain the differences between hardlinks and symbolic links, including their behavior with files and directories. Explore how umask and ulimit govern file permissions and the resources available to processes.

Explore Linux LVM concepts, including maximum volume groups, online extension of logical volumes and pvscan for scanning new disks, and note that reducing requires unmounting.

Explore the Linux LVM workflow by creating physical volumes, forming a volume group and logical volume, formatting and mounting the file system, and extending it.

Extend the Linux file system and its logical volume online, with steps to check space in the volume group and resize the logical volume; note that reducing requires unmounting.

Learn how to safely reduce a logical volume: unmount the filesystem, shrink the filesystem, then reduce the logical volume, check for errors, and verify the new size.

Scan disks to identify existing volume groups and LVM components, then learn how to activate, deactivate, unmount, and remove logical volumes and volume groups during maintenance.

Explore practical LVM concepts, including logical volumes, volume groups, and physical volumes, and learn how to list, rename, back up configurations, and use LVM dumb for diagnostics.

Trace the Linux boot sequence from BIOS to bootloader to kernel loaded in memory, then init starts the first script via rc.d and runlevels control startup.

Explore an overview of RHEL 7, its new features, and how systemd differentiates itself from other init systems. Understand the building process of RHEL 7.

Explore systemd, the modern init system that replaces init in Linux, detailing on-demand service startup, parallelization, and dependency management for faster boot and robust service control.

Explore systemd features such as boot logging, explicit dependency handling, cgroups for service isolation, and unit-based activation with targets, sockets, mounts, and timers.

Explore the boot sequence of RHEL 7, from BIOS to bootloader and kernel, then systemd initialization and the role of graphical.target and multi-user.target in starting services.

Explore the BIOS and the master boot record, their roles in Linux boot, and how grub and grub2 load the kernel from initramfs and boot partitions.

Define initramfs and its role in Linux boot, enabling drivers and filesystem mounting before the main system starts, and highlight systemd on-demand startup and boot logging.

Learn how to boot a RHEL 6 system into rescue mode using a CD, mount filesystems, and repair critical files, then switch between graphical and multi-user targets.

Boot a RHEL 7 system into rescue mode, a single-user environment requiring the root password and mounting local filesystems for repair without network or multi-user access.

Learn how to boot a RHEL 7 system into emergency mode for repair, using a minimal read-only environment with only essential services and no local mounts or network services.

Discover ssh basics for linux: secure remote login, default port 22, sshd_config, disabling root, allowing specific users, and ssh vs telnet differences with debugging -v.

Explore secure copy (scp) for transferring files between hosts, including how to automate authentication with scripts, using a username and password, and how Blowfish encryption can speed up transfers.

Explore practical linux interview topics: limiting scp bandwidth with -l to 128 bytes per second, enabling passwordless ssh keys, and copying files over a specific port with scp -P.

Define a process as a set of instructions loaded in memory, show how to identify its process id and parent, and list processes with ps commands, including custom properties.

This lecture explains process management, detailing process ids, parent and child processes, and demonstrates how killing a parent terminates its child processes through terminal examples.

Explore how Linux nice value sets process priority, including negative values, with practical examples using the nice command, and observe process states via ps and top.

Explore uninterruptible sleep mode (D state) and how a busy disk can stall a backup process. Learn paging from physical memory to SAP memory as memory usage crosses 70–80 percent.

Examine linux 7 features vs 6, including default xfs versus ext4, kernel 3.10 vs 2.6, the shift to targets, and uid ranges starting at 2000 versus 500.

Explore Linux file systems and partitioning concepts, including ext4 resizing, fsck, LVM, primary and extended partition limits, Grub boot options, and systemd service management.

Explore features of Linux 7 versus Linux 6, covering bonding, network time synchronization, file naming, and improved temp file management on Red Hat Enterprise Linux server.

Master advanced LVM concepts, metadata handling, and disk recovery from virtual machines, including restoring metadata, managing volume groups, and ensuring physical volumes remain consistent.

Explore how to recover metadata for a missing or overwritten physical volume in an lvm setup, using the volume group’s configuration file and backups to restore the system.

Practice linux logical volume management by creating physical volumes, volume groups, and logical volumes, formatting and mounting file systems, and recovering from disk failures with metadata, backups, and vendor replacement.

Explore how grub and bootloaders orchestrate Linux boot, from BIOS power-on self-test to loading the kernel, mounting the root filesystem, and launching systemd.

Learn how to boot into grub, select the kernel and initramfs, boot the latest kernel by default, and access rescue or multi-user modes, with hands-on kernel selection.

Learn to access the Grub menu, select and boot different kernels, enable rescue or emergency modes, and modify boot parameters to troubleshoot a Linux system.

Do not edit the default file directly; edit the group configuration file instead and apply changes with the provided command so they reflect in the current group settings.

Lab session on Linux QA demonstrates editing the grub defaults to add boot parameters, such as console settings, then regenerating the grub config and validating the changes.

Protect grub by setting a boot loader password to block single-user mode and console access; generate an encrypted password and update grub, then reboot to verify.