Skip to content

Commit

Permalink
fix: add dns search record limit note. (#18913)
Browse files Browse the repository at this point in the history
  • Loading branch information
Colstuwjx authored Feb 7, 2020
1 parent ecda7af commit b9ff4f1
Showing 1 changed file with 1 addition and 8 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -258,14 +258,7 @@ Kubernetes installs do not configure the nodes' `resolv.conf` files to use the
cluster DNS by default, because that process is inherently distribution-specific.
This should probably be implemented eventually.

Linux's libc is impossibly stuck ([see this bug from
2005](https://bugzilla.redhat.com/show_bug.cgi?id=168253)) with limits of just
3 DNS `nameserver` records and 6 DNS `search` records. Kubernetes needs to
consume 1 `nameserver` record and 3 `search` records. This means that if a
local installation already uses 3 `nameserver`s or uses more than 3 `search`es,
some of those settings will be lost. As a partial workaround, the node can run
`dnsmasq` which will provide more `nameserver` entries, but not more `search`
entries. You can also use kubelet's `--resolv-conf` flag.
Linux's libc (a.k.a. glibc) has a limit for the DNS `nameserver` records to 3 by default. What's more, for the glibc versions which are older than glic-2.17-222 ([the new versions update see this issue](https://access.redhat.com/solutions/58028)), the DNS `search` records has been limited to 6 ([see this bug from 2005](https://bugzilla.redhat.com/show_bug.cgi?id=168253)). Kubernetes needs to consume 1 `nameserver` record and 3 `search` records. This means that if a local installation already uses 3 `nameserver`s or uses more than 3 `search`es while your glibc versions in the affected list, some of those settings will be lost. For the workaround of the DNS `nameserver` records limit, the node can run `dnsmasq` which will provide more `nameserver` entries, you can also use kubelet's `--resolv-conf` flag. For fixing the DNS `search` records limit, consider upgrading your linux distribution or glibc version.

If you are using Alpine version 3.3 or earlier as your base image, DNS may not
work properly owing to a known issue with Alpine.
Expand Down

0 comments on commit b9ff4f1

Please sign in to comment.