What entry can be added to the syslog.conf file to have all syslog messages generated by a system displayed on console 12?
Correct Answer: A
The entry that can be added to the syslog.conf file to have all syslog messages generated by a system displayed on console 12 is A. . /dev/tty12. This entry consists of a selector field and an action field, separated by a space or a tab. The selector field specifies the pattern of facilities and priorities that match the action. The action field specifies the destination where the matching messages are sent. In this case, the selector field is ., which means all facilities and all priorities. The action field is /dev/tty12, which is the device file for the console 12. This means that any syslog message generated by the system will be displayed on the console 12, regardless of its facility or priority. This can be useful for debugging or monitoring purposes, but it can also be very noisy and distracting, as it will show all kinds of messages, including debug, info, notice, warning, err, crit, alert, and emerg12. The other options are not correct. Option B. /var/log/messages | /dev/tty12 is invalid, as it uses a pipe (|) character in the selector field, which is not allowed. The pipe character can only be used in the action field to indicate that the matching messages are piped to an external program1. Option C. | /dev/tty12 is also invalid, as it has an empty selector field, which is not allowed. The selector field must specify at least one facility and one priority1. Option D. syslog tty12 is also invalid, as it has a missing period (.) between the facility and the priority in the selector field, and a missing slash (/) before the device file in the action field. The correct syntax for this option would be syslog.* /dev/tty12, which would display only the messages with the syslog facility and any priority on the console 121. Option E. mail.* /dev/tty12 is valid, but it would not display allsyslog messages generated by a system, but only the messages with the mail facility and any priority on the console 12. This would exclude the messages from other facilities, such as auth, cron, daemon, kern, user, etc1. References: 1: syslog.conf (5) - Linux man page 2: Beginner's Guide to Syslogs in Linux [Real World Examples]
Question 77
Suppose that the command netstat -a hangs for a long time without producing output. You might suspect:
Correct Answer: B
Question 78
What is the purpose of the command mailq?
Correct Answer: B
Question 79
Which of the following information is stored in /etc/shadow for each user?
Correct Answer: C
The /etc/shadow file is a text file that stores encrypted passwords, along with user name, password expiration values, and last password change date. The credential information in the shadow file is encrypted using a one-way hash function to disable decryption. The /etc/shadow file contains one entry per line for each user listed in /etc/passwd file. Each line of the /etc/shadow file contains nine comma-separated fields, and the second field is the encrypted password of the user. The password field uses the $type$salt$hashed format, where $type is the method of cryptographic hash algorithm, salt is a random string, and hashed is the result of applying the hash function to the user's password and the salt. The /etc/shadow file is only readable by the root user, and it is used to enhance the security and control of user passwords. The other information listed are not stored in /etc/shadow file, but in /etc/passwd file. The /etc/passwd file is a text file that contains basic information about each user account on the system. Each line of the /etc/passwd file contains seven colon-separated fields, and they are: * Username: The name of the user account. * Password: An x character indicates that the encrypted password is stored in /etc/shadow file. * User ID (UID): The numerical identifier of the user account. * Group ID (GID): The numerical identifier of the primary group of the user account. * User ID Info: The comment field that can store additional information about the user, such as full name, phone number, etc. * Home Directory: The absolute path to the user's home directory, where the user's personal files and settings are stored. * Shell: The absolute path to the user's default login shell, which is the program that runs when the user logs in to the system. References: * Understanding the /etc/shadow File | Linuxize * Understanding /etc/shadow file format on Linux - nixCraft * /etc/shadow file format | Linux# * [/etc/passwd file format | Linux#]
Question 80
Which of the following lines are valid in the file /etc/hosts? (Choose TWO correct answers.)
Correct Answer: A,C
The valid lines in the file /etc/hosts are A and C. The format of the /etc/hosts file is as follows12: IP_address canonical_hostname [aliases...] where IP_address is the IPv4 or IPv6 address of the host, canonical_hostname is the official name of the host, and aliases are optional alternative names for the host. Each field is separated by whitespace (spaces or tabs). The # character indicates the beginning of a comment, and the rest of the line is ignored. The lines B, D, and E are invalid because they do not follow the format of the /etc/hosts file. Line B has the hostname and aliases before the IP address, which is incorrect. Line D has multiple IP addresses and hostnames separated by commas, which is also incorrect. Line E has two IP addresses for the same host, which is not supported by the /etc/hosts file. If a host has more than one IP address, it should have a separate line for each address3. References: * 1: hosts(5) - Linux manual page - man7.org * 2: Format of /etc/hosts on Linux (different from Windows?) * 3: hosts File Format for TCP/IP - IBM
