Troubleshooting practice questions

The root filesystem is formatted with an unsupported filesystem type.

Why wrong: This would typically produce an error message, not a hang.

The initrd image is missing from the /boot partition.

Why wrong: An initrd is not always required; the kernel can mount root directly.

The GRUB bootloader is not installed on the MBR.

Why wrong: This would prevent the bootloader from loading entirely, not cause a hang at root mount.

nsenter -t 1234 -n ip addr show

Why wrong: Requires process PID; not for named namespace.

unshare -n ip addr show

Why wrong: Creates new namespace, does not use existing one.

ip netns add ns1

Why wrong: Only adds namespace, does not execute command.

verbose

Why wrong: Not a standard kernel parameter; most kernels ignore it.

quiet

Why wrong: Suppresses most kernel messages, opposite of verbose.

The kernel image is missing.

Why wrong: Missing kernel would prevent any boot messages.

The kernel lacks SATA driver support.

Why wrong: Most kernels include SATA drivers.

The initramfs was not regenerated after adding the disk.

Why wrong: Initramfs regeneration is not required for an additional disk unless the root filesystem changes.

Run lsblk to list all block devices.

Why wrong: lsblk only lists devices already recognized by the kernel.

Check dmesg output for errors.

Why wrong: dmesg is useful after lspci to diagnose driver issues.

Run fdisk -l /dev/nvme0n1 to probe the drive.

Why wrong: fdisk requires the device to be present.

The share path /srv/share does not exist or has incorrect permissions.

Why wrong: While a missing path could cause issues, the most common cause is the lack of Samba password; also the exhibit does not indicate this.

The parameter 'read only = no' is misspelled; it should be 'writable = yes'.

Why wrong: 'read only = no' and 'writable = yes' are equivalent; both are valid and work.

The valid users list must use group names with '@' prefix, not individual names.

Why wrong: Individual user names are perfectly valid in valid users.

tcpdump -i eth0 icmp6

Why wrong: While this can capture neighbor solicitation/advertisements, it is not a quick verification tool.

traceroute6

Why wrong: traceroute6 tests path, but not neighbor discovery for the first hop.

ndp -n

Why wrong: ndp is a FreeBSD command, not available on Linux.

iptables

Why wrong: iptables is a firewall, not a capture tool.

netstat

Why wrong: netstat displays network connections and statistics, not packet capture.

nmap

Why wrong: nmap is a network scanner, not a packet capture tool.

traceroute6 -i eth0 fe80::1

Why wrong: traceroute6 traces route, does not test reachability.

ping6 fe80::1

Why wrong: Link-local addresses require interface specification.

ping -6 eth0 fe80::1

Why wrong: Incorrect syntax; ping6 is the correct command.

mod_status

Why wrong: mod_status provides server status and does not significantly impact performance.

mod_include

Why wrong: Server-side includes have low overhead and are not typically a major performance concern.

init=/bin/sh

Why wrong: init= specifies a different init program, not the root device.

rescue

Why wrong: rescue is not a standard kernel parameter.

single

Why wrong: single boots into single-user mode, but does not change the root device.

journalctl -f

Why wrong: journalctl -f follows all system logs, not only kernel messages, and may not show early boot messages.

tail -f /var/log/kern.log

Why wrong: tail -f follows a log file, but kernel messages are not always written to /var/log/kern.log immediately or at all.

less /var/log/messages

Why wrong: less views a static file, not real-time.

The initramfs for the new kernel was not generated

Why wrong: Missing initramfs typically results in a kernel panic with a VFS error, not a blank screen.

Secure Boot is enabled and the new kernel is not signed

Why wrong: Secure Boot signature issues prevent the kernel from loading altogether, usually with an error message.

The new kernel's root= parameter points to an invalid device

Why wrong: An invalid root parameter would cause a kernel panic with a mount error, not a blank screen.

Generate a new RSA key pair on the client with ssh-keygen.

Why wrong: Existing key is supposed to be correct.

Run 'ssh-add' to add the private key to the SSH agent.

Why wrong: Agent not needed if key is directly used.

Restart the sshd service on the client.

Why wrong: Client daemon not involved.

systemctl restart networking

Why wrong: Restarting networking may disrupt other services and might not trigger a DHCP renewal if the interface is already configured.

ip route del default

Why wrong: This would only remove any existing default route, but there is no default route to remove, and it does not add one.

ip route add default via 192.168.1.1

Why wrong: While this would add a default route manually, it is not the appropriate resolution for a DHCP configuration issue; the route should be assigned automatically by DHCP.