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Copying Files to or from a Container

Important

Azure Red Hat OpenShift 3.11 will be retired 30 June 2022. Support for creation of new Azure Red Hat OpenShift 3.11 clusters continues through 30 November 2020. Following retirement, remaining Azure Red Hat OpenShift 3.11 clusters will be shut down to prevent security vulnerabilities.

Follow this guide to create an Azure Red Hat OpenShift 4 cluster. If you have specific questions, please contact us

Overview

You can use the CLI to copy local files to or from a remote directory in a container. This is a useful tool for copying database archives to and from your pods for backup and restore purposes. It can also be used to copy source code changes into a running pod for development debugging, when the running pod supports hot reload of source files.

Basic Usage

Support for copying local files to or from a container is built into the CLI:

$ oc rsync <source> <destination> [-c <container>]

For example, to copy a local directory to a pod directory:

$ oc rsync /home/user/source devpod1234:/src

Or to copy a pod directory to a local directory:

$ oc rsync devpod1234:/src /home/user/source

Backing Up and Restoring Databases

Use oc rsync to copy database archives from an existing database container to a new database container’s persistent volume directory.

MySQL is used in the example below. Replace mysql|MYSQL with pgsql|PGSQL or mongodb|MONGODB and refer to the migration guide to find the exact commands for each of our supported database images. The example assumes an existing database container.

  1. Back up the existing database from a running database pod:

    $ oc rsh <existing db container>
# mkdir /var/lib/mysql/data/db_archive_dir
# mysqldump --skip-lock-tables -h ${MYSQL_SERVICE_HOST} -P ${MYSQL_SERVICE_PORT:-3306} \
  -u ${MYSQL_USER} --password="$MYSQL_PASSWORD" --all-databases > /var/lib/mysql/data/db_archive_dir/all.sql
# exit

  2. Remote sync the archive file to your local machine:

    $ oc rsync <existing db container with db archive>:/var/lib/mysql/data/db_archive_dir /tmp/.

  3. Start a second MySQL pod into which to load the database archive file created above. The MySQL pod must have a unique DATABASE_SERVICE_NAME.

    $ oc new-app mysql-persistent \
  -p MYSQL_USER=<archived mysql username> \
  -p MYSQL_PASSWORD=<archived mysql password> \
  -p MYSQL_DATABASE=<archived database name> \
  -p DATABASE_SERVICE_NAME='mysql2' (1)
$ oc rsync /tmp/db_archive_dir new_dbpod1234:/var/lib/mysql/data
$ oc rsh new_dbpod1234
    1 mysql is the default. In this example, mysql2 is created.

  4. Use the appropriate commands to restore the database in the new database container from the copied database archive directory:

    MySQL
    $ cd /var/lib/mysql/data/db_archive_dir
$ mysql -u root
$ source all.sql
$ GRANT ALL PRIVILEGES ON <dbname>.* TO '<your username>'@'localhost'; FLUSH PRIVILEGES;
$ cd ../; rm -rf /var/lib/mysql/data/db_backup_dir

    You now have two MySQL database pods running in your project with the archived database.

Requirements

The oc rsync command uses the local rsync command if present on the client’s machine. This requires that the remote container also have the rsync command.

If rsync is not found locally or in the remote container, then a tar archive will be created locally and sent to the container where tar will be used to extract the files. If tar is not available in the remote container, then the copy will fail.

The tar copy method does not provide the same functionality as rsync. For example, rsync creates the destination directory if it does not exist and will only send files that are different between the source and the destination.

In Windows, the cwRsync client should be installed and added to the PATH for use with the oc rsync command.

Specifying the Copy Source

The source argument of the oc rsync command must point to either a local directory or a pod directory. Individual files are not currently supported.

When specifying a pod directory the directory name must be prefixed with the pod name:

<pod name>:<dir>

Just as with standard rsync, if the directory name ends in a path separator (/), only the contents of the directory are copied to the destination. Otherwise, the directory itself is copied to the destination with all its contents.

Specifying the Copy Destination

The destination argument of the oc rsync command must point to a directory. If the directory does not exist, but rsync is used for copy, the directory is created for you.

Deleting Files at the Destination

The --delete flag may be used to delete any files in the remote directory that are not in the local directory.

Continuous Syncing on File Change

Using the --watch option causes the command to monitor the source path for any file system changes, and synchronizes changes when they occur. With this argument, the command runs forever.

Synchronization occurs after short quiet periods to ensure a rapidly changing file system does not result in continuous synchronization calls.

When using the --watch option, the behavior is effectively the same as manually invoking oc rsync repeatedly, including any arguments normally passed to oc rsync. Therefore, you can control the behavior via the same flags used with manual invocations of oc rsync, such as --delete.

Advanced Rsync Features

The oc rsync command exposes fewer command line options than standard rsync. In the case that you wish to use a standard rsync command line option which is not available in oc rsync (for example the --exclude-from=FILE option), it may be possible to use standard rsync 's --rsh (-e) option or RSYNC_RSH environment variable as a workaround, as follows:

$ rsync --rsh='oc rsh' --exclude-from=FILE SRC POD:DEST

or:

$ export RSYNC_RSH='oc rsh'
$ rsync --exclude-from=FILE SRC POD:DEST

Both of the above examples configure standard rsync to use oc rsh as its remote shell program to enable it to connect to the remote pod, and are an alternative to running oc rsync.