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Properly handle containers which pre-date the resolv.conf update feature
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)
Phil Estes authored on 2015/01/10 11:18:57Showing 2 changed files
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@@ -1057,7 +1057,15 @@ func (container *Container) updateResolvConf(updatedResolvConf []byte, newResolv |
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//read the hash from the last time we wrote resolv.conf in the container |
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hashBytes, err := ioutil.ReadFile(resolvHashFile) |
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if err != nil {
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- return err |
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+ if !os.IsNotExist(err) {
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+ return err |
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+ } |
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+ // backwards compat: if no hash file exists, this container pre-existed from |
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+ // a Docker daemon that didn't contain this update feature. Given we can't know |
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+ // if the user has modified the resolv.conf since container start time, safer |
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+ // to just never update the container's resolv.conf during it's lifetime which |
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+ // we can control by setting hashBytes to an empty string |
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+ hashBytes = []byte("")
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} |
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//if the user has not modified the resolv.conf of the container since we wrote it last |
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@@ -201,6 +201,13 @@ If the options (`--dns` or `--dns-search`) have been used to modify the |
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default host configuration, then the replacement with an updated host's |
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`/etc/resolv.conf` will not happen as well. |
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+> **Note**: |
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+> For containers which were created prior to the implementation of |
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+> the `/etc/resolv.conf` update feature in Docker 1.5.0: those |
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+> containers will **not** receive updates when the host `resolv.conf` |
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+> file changes. Only containers created with Docker 1.5.0 and above |
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+> will utilize this auto-update feature. |
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+ |
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## Communication between containers and the wider world |
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<a name="the-world"></a> |