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Properly handle containers which pre-date the resolv.conf update feature

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This fixes the container start issue for containers which were started
on a daemon prior to the resolv.conf updater PR. The update code will
now safely ignore these containers (given they don't have a sha256 hash
to compare against) and will not attempt to update the resolv.conf
through their lifetime.

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
This commit is contained in:
Phil Estes 2015-01-09 21:18:57 -05:00
parent ef2d6dda0f
commit 30eff2720a
2 changed files with 16 additions and 1 deletions
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8
daemon/container.go
View file

@ -1057,8 +1057,16 @@ func (container *Container) updateResolvConf(updatedResolvConf []byte, newResolv
//read the hash from the last time we wrote resolv.conf in the container
hashBytes, err := ioutil.ReadFile(resolvHashFile)
if err != nil {
if !os.IsNotExist(err) {
return err
}
// backwards compat: if no hash file exists, this container pre-existed from
// a Docker daemon that didn't contain this update feature. Given we can't know
// if the user has modified the resolv.conf since container start time, safer
// to just never update the container's resolv.conf during it's lifetime which
// we can control by setting hashBytes to an empty string
hashBytes = []byte("")
}
//if the user has not modified the resolv.conf of the container since we wrote it last
//we will replace it with the updated resolv.conf from the host

7
docs/sources/articles/networking.md
View file

@ -201,6 +201,13 @@ If the options (`--dns` or `--dns-search`) have been used to modify the
default host configuration, then the replacement with an updated host's
`/etc/resolv.conf` will not happen as well.
> **Note**:
> For containers which were created prior to the implementation of
> the `/etc/resolv.conf` update feature in Docker 1.5.0: those
> containers will **not** receive updates when the host `resolv.conf`
> file changes. Only containers created with Docker 1.5.0 and above
> will utilize this auto-update feature.
## Communication between containers and the wider world
<a name="the-world"></a>