Access log configuration in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable access logging in nginx.

Nginx

access_log [1];

Drag options to blanks, or click blank then click option'

A/etc/nginx/nginx.conf

B/var/log/nginx/access.log

C/usr/share/nginx/html

D/var/log/nginx/error.log

Attempts:

3 left

💡 Hint

Common Mistakes

Using the error log path instead of the access log path.

Specifying a directory instead of a file path.

The access_log directive specifies the file where nginx writes access logs. The default and common path is /var/log/nginx/access.log.

2fill in blank

medium

Complete the code to disable access logging in nginx.

Nginx

access_log [1];

Drag options to blanks, or click blank then click option'

Aoff

B/var/log/nginx/access.log

Con

D/var/log/nginx/error.log

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'on' instead of 'off' to disable logging.

Providing a file path when intending to disable logging.

Setting access_log off; disables access logging in nginx.

3fill in blank

hard

Fix the error in the access log format definition.

Nginx

log_format main '[1]';

Drag options to blanks, or click blank then click option'

A$remote_addr $remote_user $time_local $request $status $body_bytes_sent $http_referer $http_user_agent

Bremote_addr - remote_user [time_local] "request" status body_bytes_sent "http_referer" "http_user_agent"

C$remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent"

D$remote_addr - $remote_user $time_local $request $status $body_bytes_sent $http_referer $http_user_agent

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the dollar signs before variables.

Missing quotes or brackets around parts of the log format.

The correct log format uses variables with $ and includes quotes and brackets exactly as shown in option C.

4fill in blank

hard

Fill both blanks to configure nginx to use the custom log format and specify the log file.

Nginx

access_log [1] [2];

Drag options to blanks, or click blank then click option'

A/var/log/nginx/custom_access.log

Bmain

Cdefault

D/var/log/nginx/access.log

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of file path and format name.

Using the default log file instead of the custom one.

The access_log directive takes the log file path first, then the log format name.

5fill in blank

hard

Fill all three blanks to create a conditional access log that logs only requests with status code 404.

Nginx

map $status $log_404 {
    default 0;
    [1] 1;
}

access_log [2] [3] if=$log_404;

Drag options to blanks, or click blank then click option'

A404

B/var/log/nginx/404.log

Cmain

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong status code in the map block.

Not using the if condition in access_log.

Mixing up the log file path and format name.

The map block sets $log_404 to 1 only when status is 404. The access_log directive uses this variable in the if condition to log only those requests.

Practice

1. What is the main purpose of the access_log directive in nginx?

easy

A. To record details of every request made to the server

B. To block unwanted IP addresses

C. To restart the nginx service

D. To configure server SSL certificates

Solution

1. Step 1: Understand the role of access logs

   Access logs keep track of every request made to the server, helping monitor traffic and troubleshoot issues.

2. Step 2: Identify the function of access_log

   The access_log directive in nginx specifies where and how these request details are recorded.

3. Final Answer:

   To record details of every request made to the server -> Option A

4. Quick Check:

   Access logs = record requests [OK]

Hint: Access logs always record requests, not block or restart [OK]

Common Mistakes:

• Confusing access_log with security or restart commands
• Thinking access_log blocks IPs
• Assuming access_log manages SSL

2. Which of the following is the correct syntax to enable access logging to a file named /var/log/nginx/access.log with the default format?

easy

A. access_log /var/log/nginx/access.log off;

B. access_log /var/log/nginx/access.log default;

C. access_log /var/log/nginx/access.log main;

D. access_log /var/log/nginx/access.log;

Solution

1. Step 1: Recall default access_log syntax

   The access_log directive requires the log file path and optionally a format. If no format is given, the default is used.

2. Step 2: Analyze each option

   access_log /var/log/nginx/access.log main; uses 'main' which is predefined but different from the default 'combined'; access_log /var/log/nginx/access.log default; uses 'default' which is not a valid format name; access_log /var/log/nginx/access.log; correctly specifies only the file path, using default format implicitly; access_log /var/log/nginx/access.log off; disables logging with 'off'.

3. Final Answer:

   access_log /var/log/nginx/access.log; -> Option D

4. Quick Check:

   Default format = omit format name [OK]

Hint: Omit format name to use default logging [OK]

Common Mistakes:

• Using invalid format names like 'default'
• Adding 'off' disables logging
• Using 'main' which is not the default format

3. Given this nginx config snippet:

access_log /var/log/nginx/access.log custom_format;
log_format custom_format '$remote_addr - $remote_user [$time_local] "$request" $status';

What will be logged for a request from IP 192.168.1.10 with user 'john' requesting GET /home and status 200?

medium

A. john - 192.168.1.10 [time] "GET /home" 200

B. 192.168.1.10 - john [time] "GET /home" 200

C. 192.168.1.10 - - [time] "GET /home" 200

D. 192.168.1.10 john [time] GET /home 200

Solution

1. Step 1: Understand the log_format string

   The format is: $remote_addr - $remote_user [$time_local] "$request" $status. This means IP, dash, username, time, request in quotes, and status code.

2. Step 2: Substitute values from the request

   IP is 192.168.1.10, user is 'john', request is 'GET /home', status is 200. Time is shown as [time] placeholder.

3. Final Answer:

   192.168.1.10 - john [time] "GET /home" 200 -> Option B

4. Quick Check:

   Format matches IP - user [time] "request" status [OK]

Hint: Match variables exactly as in log_format string [OK]

Common Mistakes:

• Mixing order of IP and user
• Omitting dashes or quotes
• Confusing $remote_user with $remote_addr

4. You configured access_log /var/log/nginx/access.log combined; but no logs appear. What is the most likely error?

medium

A. The 'combined' log format is not defined in nginx config

B. The log file path is incorrect

C. The access_log directive disables logging by default

D. Nginx does not support custom log formats

Solution

1. Step 1: Understand the 'combined' format usage

   'combined' is a common log format but must be defined with log_format directive in nginx config before use.

2. Step 2: Analyze why logs don't appear

   If 'combined' is not defined, nginx ignores the logging directive or fails silently, so no logs are written.

3. Final Answer:

   The 'combined' log format is not defined in nginx config -> Option A

4. Quick Check:

   Undefined format = no logs [OK]

Hint: Define custom formats before using them in access_log [OK]

Common Mistakes:

• Assuming 'combined' is built-in by default
• Ignoring file permission issues
• Thinking access_log disables logging by default

5. You want to log only requests with status code 400 or higher to /var/log/nginx/error_access.log and all requests to the default access log. Which configuration snippet achieves this?

hard

A. access_log /var/log/nginx/access.log;
access_log /var/log/nginx/error_access.log combined if=$status > 399;

B. access_log /var/log/nginx/access.log;
access_log /var/log/nginx/error_access.log combined if=$status >= 400;

C. map $status $log_error { ~^[4-9] 1; default 0; }
access_log /var/log/nginx/access.log;
access_log /var/log/nginx/error_access.log combined if=$log_error;

D. access_log /var/log/nginx/access.log;
access_log /var/log/nginx/error_access.log combined if=$status eq 400;

Solution

1. Step 1: Understand conditional logging in nginx

   nginx supports conditional logging using the if= parameter with variables and expressions.

2. Step 2: Use a map to create a variable for status >= 400

   Direct comparisons like '$status >= 400' are not supported in if=. Instead, a map is used to set a variable $log_error to 1 for status codes 400 and above.

3. Step 3: Apply conditional logging using the variable

   Use if=$log_error in the access_log directive to log only those requests.

4. Final Answer:

   map $status $log_error { ~^[4-9] 1; default 0; } access_log /var/log/nginx/access.log; access_log /var/log/nginx/error_access.log combined if=$log_error; -> Option C

5. Quick Check:

   Conditional logging requires map + if= variable [OK]

Hint: Use map to create condition variable for logging [OK]

Common Mistakes:

• Trying to use direct comparison in if= condition
• Not defining a map for conditional logging
• Expecting nginx to parse expressions in if= directly