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[ Linux Command Encyclopaedia](#)\n\n* * *\n\ndig (Domain Information Groper) is a powerful DNS query tool in Linux systems, used to query DNS name servers. Compared with the traditional nslookup, dig provides more detailed query results and more flexible query options.\n\nMain features of dig command:\n\n* Displays the complete DNS query process\n* Supports all DNS record type queries\n* Allows specifying a particular DNS server to query\n* Output format is clear and easy to read\n\n* * *\n\n## dig Command Basic Syntax\n\ndig [@server] \n### Parameter Description\n\n| Parameter | Description |\n| --- | --- |\n| `@server` | Specifies the DNS server to query (e.g., `@8.8.8.8`) |\n| `domain` | The domain name to query (e.g., `example.com`) |\n| `query-type` | The record type to query (e.g., `A`, `MX`, `NS`, etc.) |\n| `query-class` | The query class (usually `IN` for Internet) |\n| `query-options` | Additional query options |\n\n* * *\n\n## Common Query Types\n\ndig supports querying various DNS record types. Here are the common record types:\n\n| Record Type | Description | Example |\n| --- | --- | --- |\n| A | IPv4 address record | `dig example.com A` |\n| AAAA | IPv6 address record | `dig example.com AAAA` |\n| MX | Mail exchange record | `dig example.com MX` |\n| NS | Name server record | `dig example.com NS` |\n| CNAME | Canonical name record | `dig www.example.com CNAME` |\n| TXT | Text record | `dig example.com TXT` |\n| SOA | Start of authority record | `dig example.com SOA` |\n| ANY | All records | `dig example.com ANY` |\n\n* * *\n\n## dig Command Output Analysis\n\nExecute a simple dig query:\n\ndig example.com\n\nThe typical output contains the following sections:\n\n1. **HEADER section**: Displays basic information about the query\n\n * `opcode`: Operation code\n * `status`: Response status\n * `id`: Query ID\n * `flags`: Flags (such as qr, rd, ra, etc.)\n\n2. **QUESTION section**: Displays the query question\n\n * Contains the queried domain name and record type\n\n3. **ANSWER section**: Query results\n\n * Contains actual DNS record information\n\n4. **AUTHORITY section**: Authoritative name server information\n\n * Displays the authoritative DNS server responsible for the domain\n\n5. **ADDITIONAL section**: Additional information\n\n * May contain other useful information\n\n6. **STATISTICS section**: Query statistics\n\n * Displays query time, server information, etc.\n\n* * *\n\n## Practical Query Examples\n\n### 1. Query a Specific DNS Server\n\ndig @8.8.8.8 example.com\nThis command will query the A record of example.com from Google's public DNS server (8.8.8.8).\n\n### 2. Query MX Records\n\ndig example.com MX\nQuery mail server information for the domain.\n\n### 3. Query the Full Domain Resolution Process\n\ndig +trace example.com\nThe `+trace` option displays the complete resolution process starting from the root name server.\n\n### 4. Short Output Mode\n\ndig +short example.com\nOnly displays the query result without other detailed information.\n\n### 5. Reverse DNS Query\n\ndig -x 8.8.8.8\nQuery the domain name corresponding to an IP address.\n\n### 6. Batch Query Multiple Domain Names\n\ndig -f domains.txt +short\nWhere domains.txt contains the list of domain names to query, one per line.\n\n* * *\n\n## Advanced Options\n\n### 1. Control Output Format\n\ndig +noall +answer example.com\n`+noall` hides all sections, `+answer` only displays the ANSWER section.\n\n### 2. Set Query Timeout\n\ndig +time=5 example.com\nSets the query timeout to 5 seconds.\n\n### 3. Specify Query Port\n\ndig @dns.server.example.com -p 5353 example.com\nQuery the DNS server on a non-standard port (5353).\n\n### 4. Display TTL Information\n\ndig +ttlid example.com\nDisplays the TTL (Time To Live) value of the record.\n\n### 5. Display Query Statistics\n\ndig +stats example.com\nDisplays detailed query statistics.\n\n* * *\n\n## Frequently Asked Questions\n\n### 1. What is the difference between dig and nslookup?\n\ndig provides more detailed output and more query options than nslookup, making it a more professional DNS query tool. nslookup has been gradually replaced by dig.\n\n### 2. How to install the dig command?\n\nIn most Linux distributions, dig is part of the bind-utils or dnsutils package:\n\n* Debian/Ubuntu:\n\nsudo apt install dnsutils\n* CentOS/RHEL:\n\nsudo yum install bind-utils\n\n### 3. Why does my dig query not return an ANSWER section?\n\nPossible reasons:\n\n* The queried record type does not exist\n* The domain name does not exist\n* The DNS server does not have records for this domain\n* Network connection issues\n\nYou can try using the `+trace` option to view the complete resolution process.\n\n* * *\n\n## Practical Application Scenarios\n\n### 1. Troubleshoot DNS Resolution Issues\n\nWhen a website cannot be accessed, you can use dig to check if DNS resolution is working normally:\n\ndig +trace example.com\n### 2. Check Mail Server Configuration\n\nVerify whether the domain's mail server configuration is correct:\n\ndig example.com MX\n### 3. Monitor DNS Record Changes\n\nBy periodically executing dig queries and comparing results, you can monitor changes in DNS records:\n\n## Example\n\ndig example.com A |grep -v ";" > current.txt\n\ndiff current.txt previous.txt\n\n### 4. Test DNS Server Response Time\n\nCompare the response speed of different DNS servers:\n\n## Example\n\ntime dig @8.8.8.8 example.com\n\ntime dig @1.1.1.1 example.com\n\n* * *\n\n## Summary\n\nThe dig command is an essential DNS diagnostic tool for Linux system administrators and network engineers. Through learning this article, you should be able to:\n\n1. Understand the basic syntax and common options of the dig command\n2. Query various types of DNS records\n3. Analyze the output of the dig command\n4. Use dig to solve actual DNS-related problems\n5. Master the advanced usage and techniques of dig\n\nTo learn more about the dig command, you can view its manual page:\n\nman dig\nOr use the help option:\n\ndig -h\n\n* * Linux Command Encyclopaedia](#)