102-500試験無料問題集「Lpi LPIC-1 Exam 102, Part 2 of 2, version 5.0 認定」
What command is used to add OpenSSH private keys to a running ssh-agen . instance? (Specify the command name only without any path.)
正解：
sshadd
Which option in the /etc/ntp.conf file specifies an external NTP source to be queried for time information? (Specify ONLY the option without any values or parameters.)
正解：
server
Explanation:
The server option is used to configure a persistent association with a remote server or peer. It takes an argument that is either a host name or a numeric IP address of the NTP server. The ntpd daemon will periodically send NTP packets to the specified server and adjust the local clock according to the received responses. Multiple server options can be used to specify more than one NTP source. For example, the following lines in the /etc/ntp.conf file configure four external NTP sources:
server 0.asia.pool.ntp.org
server 0.oceania.pool.ntp.org
server 0.europe.pool.ntp.org
server 0.north-america.pool.ntp.org
Reference:
https://docs.ntpsec.org/latest/ntp_conf.html
https://vceguide.com/which-option-in-the-etc-ntp-conf-file-specifies-an-external-ntp-source-to-be-queried-for-time-information-2/
https://vceguide.com/which-option-in-the-etcntp-conf-file-specifies-an-external-ntp-source-to-be-queried-for-time-information/
Explanation:
The server option is used to configure a persistent association with a remote server or peer. It takes an argument that is either a host name or a numeric IP address of the NTP server. The ntpd daemon will periodically send NTP packets to the specified server and adjust the local clock according to the received responses. Multiple server options can be used to specify more than one NTP source. For example, the following lines in the /etc/ntp.conf file configure four external NTP sources:
server 0.asia.pool.ntp.org
server 0.oceania.pool.ntp.org
server 0.europe.pool.ntp.org
server 0.north-america.pool.ntp.org
Reference:
https://docs.ntpsec.org/latest/ntp_conf.html
https://vceguide.com/which-option-in-the-etc-ntp-conf-file-specifies-an-external-ntp-source-to-be-queried-for-time-information-2/
https://vceguide.com/which-option-in-the-etcntp-conf-file-specifies-an-external-ntp-source-to-be-queried-for-time-information/
In which file, if present, must all users be listed that are allowed to use the cron scheduling system? (Specify the full name of the file, including path.)
正解：
etccronallow
Explanation:
The /etc/cron.allow file is a file that contains a list of users who are allowed to use the cron scheduling system. The cron scheduling system is a way of running commands or scripts at specified times or intervals. Users can create their own cron jobs by using the crontab command, which edits a file called crontab that stores the user's scheduled tasks. However, not all users may have access to the crontab command or the cron system. The access is controlled by two files: /etc/cron.allow and /etc/cron.deny. If the /etc/cron.allow file exists, then only the users listed in this file can use the crontab command and the cron system. The file should have one user name per line. If the /etc/cron.allow file does not exist, then the /etc/cron.deny file is checked. If this file exists, then the users listed in this file are denied access to the crontab command and the cron system. If neither file exists, then the access depends on the configuration of the cron daemon, which is the program that runs the cron jobs. By default, only the root user can use the cron system if no files exist. The root user can always use the cron system regardless of the existence or content of these files. To create or edit the /etc/cron.allow file, the root user needs to use a text editor such as vi, nano, or emacs. For example, to allow the users alice and bob to use the cron system, the root user can use the following command:
sudo vi /etc/cron.allow
And then add the following lines to the file:
alice bob
And then save and exit the file. Reference:
How cron.allow and cron.deny can be used to limit access to crontab for ...
/etc/cron.allow - Linux Bash Shell Scripting Tutorial Wiki
Linux / UNIX Restrict at / cron Usage To Authorized Users
Explanation:
The /etc/cron.allow file is a file that contains a list of users who are allowed to use the cron scheduling system. The cron scheduling system is a way of running commands or scripts at specified times or intervals. Users can create their own cron jobs by using the crontab command, which edits a file called crontab that stores the user's scheduled tasks. However, not all users may have access to the crontab command or the cron system. The access is controlled by two files: /etc/cron.allow and /etc/cron.deny. If the /etc/cron.allow file exists, then only the users listed in this file can use the crontab command and the cron system. The file should have one user name per line. If the /etc/cron.allow file does not exist, then the /etc/cron.deny file is checked. If this file exists, then the users listed in this file are denied access to the crontab command and the cron system. If neither file exists, then the access depends on the configuration of the cron daemon, which is the program that runs the cron jobs. By default, only the root user can use the cron system if no files exist. The root user can always use the cron system regardless of the existence or content of these files. To create or edit the /etc/cron.allow file, the root user needs to use a text editor such as vi, nano, or emacs. For example, to allow the users alice and bob to use the cron system, the root user can use the following command:
sudo vi /etc/cron.allow
And then add the following lines to the file:
alice bob
And then save and exit the file. Reference:
How cron.allow and cron.deny can be used to limit access to crontab for ...
/etc/cron.allow - Linux Bash Shell Scripting Tutorial Wiki
Linux / UNIX Restrict at / cron Usage To Authorized Users
Which file, if present, must contain all users that are allowed to use the cron scheduling system? (Specify the full name of the file, including path.)
正解：
crontab
Explanation:
The file /etc/cron.allow, if present, must contain all users that are allowed to use the cron scheduling system. This file is used to restrict the access to cron for security reasons. Only users listed in this file can create and edit their own crontab files using the crontab command. If the file does not exist, all users can use cron, unless the file /etc/cron.deny exists, which lists the users that are not allowed to use cron12. Reference: 1: Cron and Crontab usage and examples. 2: How to use cron in Linux.
Explanation:
The file /etc/cron.allow, if present, must contain all users that are allowed to use the cron scheduling system. This file is used to restrict the access to cron for security reasons. Only users listed in this file can create and edit their own crontab files using the crontab command. If the file does not exist, all users can use cron, unless the file /etc/cron.deny exists, which lists the users that are not allowed to use cron12. Reference: 1: Cron and Crontab usage and examples. 2: How to use cron in Linux.
Which environment variable should be set in order to change the time zone for the commands run from within the environment variable's scope? (Specify the variable name only.)
正解：
TZ
Explanation:
The TZ environment variable is used to change the time zone for the commands run from within the environment variable's scope. It specifies the name of a time zone as defined in the /usr/share/zoneinfo directory or a custom time zone in the POSIX format12. The TZ variable can be set either globally in a shell profile file or locally in a shell session. For example, to set the time zone to America/New_York for the current shell session, one can use the following command:
export TZ=America/New_York
To verify the change, one can use the date command to display the current date and time according to the TZ variable. The TZ variable can also be used to run a single command with a different time zone without affecting the system's time zone. For example, to run the date command with the Asia/Tokyo time zone, one can use the following syntax:
TZ=Asia/Tokyo date
The TZ variable is useful for testing how applications behave in different time zones or for displaying the time in different locations34. Reference:
How to Set or Change the Time Zone in Linux | Linuxize
Linux / UNIX: TZ Environment Variable - nixCraft
Get Current System Time Zone in Linux | Baeldung on Linux
Setting the TZ Environment Variable on Linux | InterSystems Developer
Explanation:
The TZ environment variable is used to change the time zone for the commands run from within the environment variable's scope. It specifies the name of a time zone as defined in the /usr/share/zoneinfo directory or a custom time zone in the POSIX format12. The TZ variable can be set either globally in a shell profile file or locally in a shell session. For example, to set the time zone to America/New_York for the current shell session, one can use the following command:
export TZ=America/New_York
To verify the change, one can use the date command to display the current date and time according to the TZ variable. The TZ variable can also be used to run a single command with a different time zone without affecting the system's time zone. For example, to run the date command with the Asia/Tokyo time zone, one can use the following syntax:
TZ=Asia/Tokyo date
The TZ variable is useful for testing how applications behave in different time zones or for displaying the time in different locations34. Reference:
How to Set or Change the Time Zone in Linux | Linuxize
Linux / UNIX: TZ Environment Variable - nixCraft
Get Current System Time Zone in Linux | Baeldung on Linux
Setting the TZ Environment Variable on Linux | InterSystems Developer
Which file is processed by newaliases? (Specify the full name of the file, including path.)
正解：
etcmailalia
Which parameter of the ssh command specifies the location of the private key used for login attempts? (Specify ONLY the option name without any values or parameters.)
正解：
sshkeygen