Log format customization in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a custom log format named 'main'.

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

B$remote_addr $request_time $status

C$host $remote_addr $request

D$status $body_bytes_sent $request_time

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a format missing $remote_addr or $request

Using incomplete log variables

This is the standard custom log format that includes client IP, user, time, request, status, and bytes sent.

2fill in blank

medium

Complete the code to set the access log to use the custom format 'main'.

Nginx

access_log /var/log/nginx/access.log [1];

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

Acustom

Bcombined

Cdefault

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'combined' which is a predefined format

Using undefined format names

The access_log directive uses the custom format name 'main' to log requests.

3fill in blank

hard

Fix the error in the log_format directive to correctly include the request time.

Nginx

log_format timed '$remote_addr - $remote_user [$time_local] "$request" [1] $status';

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

A$requesttime

B$request_time

C$time_request

D$time_local

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect variable names like $time_request

Confusing $time_local with request time

The correct variable for request processing time is $request_time.

4fill in blank

hard

Fill both blanks to create a log format that logs client IP and user agent.

Nginx

log_format client_info '[1] - "$http_user_agent" [2]';

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

A$remote_addr

B$remote_user

C$request

D$status

Attempts:

3 left

💡 Hint

Common Mistakes

Using $request or $status instead of user info

Mixing variable order

The format logs the client IP ($remote_addr) and the remote user ($remote_user) along with the user agent.

5fill in blank

hard

Fill all three blanks to define a log format that logs the method, URI, and status code.

Nginx

log_format method_uri_status '[1] [2] [3]';

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

A$request_method

B$request_uri

C$status

D$remote_addr

Attempts:

3 left

💡 Hint

Common Mistakes

Including $remote_addr instead of status

Mixing variable order

This format logs the HTTP method, the requested URI, and the response status code.

Practice

1. What is the purpose of the log_format directive in nginx?

easy

A. To define a custom format for access logs

B. To specify the location of error logs

C. To enable SSL encryption for logs

D. To set the maximum size of log files

Solution

1. Step 1: Understand the role of log_format

   The log_format directive lets you create a custom pattern for how nginx records access logs.

2. Step 2: Differentiate from other logging directives

   Other directives like error_log set error log location, not format. log_format is specifically for access log formatting.

3. Final Answer:

   To define a custom format for access logs -> Option A

4. Quick Check:

   log_format = custom access log format [OK]

Hint: log_format sets how access logs look, not location [OK]

Common Mistakes:

• Confusing log_format with error_log
• Thinking log_format sets log file size
• Assuming log_format enables encryption

2. Which of the following is the correct syntax to define a custom log format named myformat that logs the client IP and request URI?

easy

A. log_format myformat = '$remote_addr $request_uri';

B. log_format myformat '$remote_addr $request_uri';

C. log_format myformat { $remote_addr $request_uri };

D. log_format myformat: '$remote_addr $request_uri';

Solution

1. Step 1: Recall correct log_format syntax

   The correct syntax uses log_format name 'format_string'; with single quotes around variables.

2. Step 2: Identify correct option

   log_format myformat '$remote_addr $request_uri'; matches this syntax exactly. Other options use invalid braces, equals, or colons.

3. Final Answer:

   log_format myformat '$remote_addr $request_uri'; -> Option B

4. Quick Check:

   Correct syntax uses single quotes and semicolon [OK]

Hint: Use single quotes and semicolon for log_format [OK]

Common Mistakes:

• Using braces {} instead of quotes
• Adding equals sign = incorrectly
• Using colon : after format name

3. Given this nginx configuration snippet:

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

What will be the output format of each log entry?

medium

A. Status code - Client IP [time] "request" user

B. User - Client IP [time] "request" status code

C. Client IP - user [time] "request" status code

D. Request - Client IP [time] "user" status code

Solution

1. Step 1: Analyze the log_format string

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

2. Step 2: Match format to options

   Client IP - user [time] "request" status code correctly describes the order and content of the log entry.

3. Final Answer:

   Client IP - user [time] "request" status code -> Option C

4. Quick Check:

   Variables order matches Client IP - user [time] "request" status code [OK]

Hint: Match variables order exactly to format string [OK]

Common Mistakes:

• Mixing order of variables
• Confusing $remote_user with $remote_addr
• Ignoring quotes around $request

4. You wrote this configuration:

log_format mylog $remote_addr - $request_uri

But nginx fails to start. What is the error?

medium

A. Missing semicolon at the end

B. Missing quotes around the log format string

C. Incorrect variable name $request_uri

D. log_format directive cannot be used in http block

Solution

1. Step 1: Check syntax requirements for log_format

   The log_format directive must end with a semicolon (;).

2. Step 2: Identify the error in given config

   The string lacks the terminating semicolon, causing a syntax error.

3. Final Answer:

   Missing semicolon at the end -> Option A

4. Quick Check:

   Semicolon terminates the directive [OK]

Hint: Every nginx directive ends with semicolon [OK]

Common Mistakes:

• Forgetting quotes around format string
• Using wrong variable names
• Omitting semicolon

5. You want to log the client IP, request method, and response time in seconds with 3 decimal places. Which custom log_format definition achieves this?

hard

A. log_format timed '$remote_addr $request_method $request_time';
access_log /var/log/nginx/timed.log timed if=$request_time;

B. log_format timed '$remote_addr $request_method $request_time sec';

C. log_format timed '$remote_addr $request_method $request_time';

D. log_format timed '$remote_addr $request_method $request_time';
access_log /var/log/nginx/timed.log timed;

Solution

1. Step 1: Define log_format with required variables

   Use $remote_addr for client IP, $request_method for method, and $request_time for response time with decimals.

2. Step 2: Apply the custom format in access_log

   To activate the format, use access_log with the format name and log file path.

3. Final Answer:

   log_format timed '$remote_addr $request_method $request_time'; access_log /var/log/nginx/timed.log timed; -> Option D

4. Quick Check:

   Define format and apply with access_log [OK]

Hint: Define format then apply with access_log [OK]

Common Mistakes:

• Not applying log_format with access_log
• Adding unnecessary text inside format
• Using invalid if condition in access_log