Fabrice Quenneville
115eec5c62
- Documented commands for flushing DNS cache using `resolvectl` and `systemd-resolve`. - Included instructions for enabling and restarting `systemd-resolved` service. - Added usage examples for `dig` and `nslookup` to query DNS records. - Provided contextual explanations and legacy tool considerations.
65 lines
1.7 KiB
Markdown
65 lines
1.7 KiB
Markdown
# DNS
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## Table of Contents
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- [DNS](#dns)
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- [Table of Contents](#table-of-contents)
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- [Flush DNS Cache](#flush-dns-cache)
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- [systemctl](#systemctl)
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- [dig](#dig)
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- [nslookup](#nslookup)
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## Flush DNS Cache
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- Clear the DNS cache to ensure that the system resolves domain names with the most up-to-date information.
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```bash
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resolvectl flush-caches
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systemd-resolve --flush-caches
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```
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- Use `resolvectl` for newer systems or `systemd-resolve` for older systems (pre-2020).
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## systemctl
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- This command enables the `systemd-resolved` service if it is not already running, ensuring DNS resolution through `systemd`.
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```bash
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systemctl enable systemd-resolved.service
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```
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**Explanation of the command:**
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- `systemd-resolve --flush-caches`: This command clears the DNS cache maintained by `systemd-resolved`, which can help resolve issues with outdated or incorrect DNS entries.
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- After flushing the cache, it may be necessary to restart the `systemd-resolved` service to ensure proper operation.
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```bash
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systemctl restart systemd-resolved
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service systemd-resolved restart
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```
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- To restart the service, use `systemctl restart systemd-resolved` (preferred). The `service` command is available but is considered legacy.
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## dig
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```bash
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dig domain.com
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dig +short NS domain.com
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```
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## nslookup
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- `nslookup` is a legacy tool but still useful for querying DNS. You can also specify custom DNS servers, such as `1.1.1.1` (Cloudflare) or `8.8.8.8` (Google), to query DNS directly without using the system’s default resolver.
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```bash
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nslookup domain.com
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nslookup -q=cname domain.com
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nslookup -q=cname domain.com 1.1.1.1
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nslookup -q=cname domain.com 8.8.8.8
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```
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```bash
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nslookup -q=mx domain.com
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nslookup -q=txt domain.com
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```
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