New Release XK0-005 Linux+ Questions

The oom-killer is invoked when the system runs out of memory, as indicated by the memory usage in the free -m output. Since swap space is not being used and physical memory is almost entirely consumed, adding more memory resources will prevent the system from running out of memory and invoking the oom-killer to terminate processes.

The best tool to use when uploading the public key to the remote servers is B. ssh-copy-id. This tool will copy the public key from the local computer to the remote server and append it to the authorized_keys file, which is used for public key authentication. This tool will also create the necessary directories and files on the remote server if they do not exist. The other tools are either not suitable or not relevant for this task. For example:

A. scp is a tool for securely copying files between hosts, but it does not automatically add the public key to the authorized_keys file.

C. ssh-agent is a tool for managing private keys and passphrases, but it does not upload the public key to the remote server.

D. ssh-keyscan is a tool for collecting public keys from remote hosts, but it does not upload the public key to the remote server.

The administrator should increase the TimeoutStartUSec configuration for the logsearch.service to resolve the issue. The output of systemct1 status logsearch.service shows that the service failed to start due to a timeout. The output of cat /etc/systemd/system/logsearch.service shows that the service has a TimeoutStartUSec configuration of 10 seconds, which might be too short for the service to start. The administrator should increase this value to a higher number, such as 30 seconds or 1 minute, and then restart the service. The other options are incorrect because they are not related to the issue. The service is already enabled, as shown by the output of systemct1 is-enabled logsearch.service. The service does not use an OnCalendar configuration, as it is not a timer unit. The service does not use a KillSignal configuration, as it is not being killed by a signal. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Processes and Scheduling Tasks, pages 434-435.

The best command to use to improve the latency issue is D. # echo ‘net.core.rmem max = 12500000’ >> /etc/sysctl.conf # echo ‘net.core.wmem_max = 12500000’ >> /etc/sysctl.conf # sysctl -p. This command will increase the size of the receive and send buffers for the network interface, which can improve the network performance and reduce packet loss. The sysctl command will apply the changes to the kernel parameters without rebooting the system.

The other commands are either incorrect or not suitable for this task. For example:

A. # echo ‘net.core.net_backlog = 5000000’ >> /etc/sysctl.conf # sysctl -p # systemctl daemon-reload will try to increase the backlog queue for incoming connections, but this is not relevant for the latency issue. The systemctl daemon-reload command is also unnecessary, as it only reloads the systemd configuration files, not the kernel parameters.

B. # ifdown eth0 # ip link set dev eth0 mtu 800 # ifup eth0 will try to change the maximum transmission unit (MTU) of the network interface to 800 bytes, but this is too low and may cause fragmentation and performance degradation. The default MTU for Ethernet is 1500 bytes, and it should not be changed unless there is a specific reason.

C. # systemctl stop network # ethtool -g eth0 512 # systemctl start network will try to change the ring buffer size of the network interface to 512, but this is too small and may cause packet drops and latency spikes. The default ring buffer size for Ethernet is usually 4096 or higher, and it should be increased if there is a high network traffic.