Backup and restore strategies in Docker - Step-by-Step Execution

Process Flow - Backup and restore strategies

Identify data to backup

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Choose backup method

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Execute backup command

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Store backup safely

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When needed, execute restore command

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Verify data restored correctly

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END

This flow shows the steps to backup Docker data and restore it when needed, ensuring data safety.

Execution Sample

Docker

docker run --rm --volumes-from mycontainer -v $(pwd):/backup busybox tar cvf /backup/backup.tar /data

docker run --rm --volumes-from mycontainer -v $(pwd):/backup busybox tar xvf /backup/backup.tar -C /data

This code backs up a Docker container's data volume to a tar file and restores it from that file.

Process Table

Step	Action	Command	Result
1	Identify data volume to backup	mycontainer volume /data	Volume /data identified
2	Run backup container to create tar	docker run --rm --volumes-from mycontainer -v $(pwd):/backup busybox tar cvf /backup/backup.tar /data	backup.tar created in current directory
3	Store backup file safely	backup.tar saved locally	Backup file ready for restore
4	Run restore container to extract tar	docker run --rm --volumes-from mycontainer -v $(pwd):/backup busybox tar xvf /backup/backup.tar -C /	Data restored into /data volume
5	Verify restored data	Check container data	Data matches backup
6	Exit	No further commands	Backup and restore complete

💡 Backup and restore process ends after data verification

Status Tracker

Variable	Start	After Backup	After Restore	Final
backup.tar	Not present	Created with container data	Used to restore data	Exists as backup file
/data volume	Has original data	Data unchanged	Replaced with restored data	Data restored successfully

Key Moments - 3 Insights

Why do we use a separate container with --volumes-from to backup data?

Because the data lives inside the container volume, the backup container accesses it via --volumes-from to copy data without stopping the original container (see execution_table step 2).

What happens if we restore data to a wrong volume path?

The restore command extracts files to the specified path. If wrong, data won't be restored correctly, causing mismatch during verification (see execution_table step 4 and 5).

Why do we mount the current directory to /backup in the container?

Mounting $(pwd) to /backup lets the container write the backup.tar file to the host machine, making it accessible outside the container (see execution_table steps 2 and 4).

Visual Quiz - 3 Questions

Look at the execution table, at which step is the backup.tar file created?

A Step 1

B Step 2

C Step 4

D Step 5

💡 Hint

Check the 'Result' column for the step where backup.tar is created.

According to the variable tracker, what is the state of /data volume after restore?

A Replaced with restored data

B Has original data

C Data unchanged

D Data lost

💡 Hint

Look at the 'After Restore' column for /data volume in variable_tracker.

If we skip mounting $(pwd) to /backup, what happens to the backup file?

A Backup fails with error

B It is saved on the host machine

C It is saved inside the container and lost after it exits

D Backup file is saved in /data volume

💡 Hint

Refer to key_moments about mounting current directory for backup file accessibility.

Concept Snapshot

Backup and restore Docker volumes:
- Use 'docker run --volumes-from' to access container volumes
- Mount host dir to container to save backup files
- Use tar to archive and extract volume data
- Verify data after restore
- Keep backups safe and test restores regularly

Full Transcript

This lesson shows how to backup and restore Docker container data volumes. First, identify the volume to backup. Then run a temporary container with --volumes-from to access the volume and mount the current directory to save the backup tar file. Use tar commands inside the container to create and extract backups. After restoring, verify the data matches the original. This method keeps data safe and allows recovery if needed.