Introduction to Dump and Restore
The dump and restore utilities are traditional Unix backup tools that work at the filesystem level. They are particularly effective for backing up and restoring ext2/ext3/ext4 filesystems.
Key Features:
- Incremental backups
- Filesystem-level backup
- Support for tape drives and other backup media
- Ability to restore individual files or entire filesystems
Note: Dump works at the filesystem level, so it must be used on unmounted filesystems or during a system maintenance period for consistent backups.
Installation
On most Linux distributions, dump and restore utilities need to be installed separately.
For Ubuntu/Debian:
sudo apt update
sudo apt install dump
For CentOS/RHEL/Fedora:
sudo yum install dump
# or
sudo dnf install dump
Verify Installation:
dump --version
restore --version
Using the Dump Utility
The dump command is used to create backups of filesystems. It supports full and incremental backups.
Basic Syntax:
dump [options] [arguments] <filesystem>
Common Options:
| Option | Description |
|---|---|
| -0 to -9 | Dump level (0 = full, 1-9 = incremental) |
| -f | Specify output file or device |
| -u | Update dump record file (/etc/dumpdates) |
| -j | Compress backup (if supported) |
| -W | Show what filesystems need to be dumped |
Example Commands:
Full backup of /home to a file:
dump -0uf /backup/home-full.dump /home
Incremental backup (level 1):
dump -1uf /backup/home-incr1.dump /home
Backup to remote server using SSH:
dump -0uf - /home | ssh user@backup-server "cat > /backup/home.dump"
Tip: Always use the -u option to update the /etc/dumpdates file, which tracks when filesystems were last backed up.
Using the Restore Utility
The restore command is used to extract files from backups created with dump.
Basic Syntax:
restore [options] [arguments]
Common Options:
| Option | Description |
|---|---|
| -r | Restore an entire filesystem |
| -x | Extract specific files or directories |
| -t | List contents of a backup |
| -f | Specify backup file |
| -i | Interactive mode |
Example Commands:
List contents of a backup:
restore -tf /backup/home-full.dump
Restore a specific file:
restore -xf /backup/home-full.dump /home/user/document.txt
Interactive restore:
restore -if /backup/home-full.dump
Important: When restoring an entire filesystem, you must restore the full backup first, then incremental backups in order.
Backup Types and Strategies
Dump supports different backup levels for implementing efficient backup strategies.
Backup Levels:
- Level 0: Full backup
- Level 1-9: Incremental backups since last same or lower level backup
Example Backup Schedule:
| Day | Backup Level | Type |
|---|---|---|
| Sunday | 0 | Full backup |
| Monday | 1 | Incremental since Sunday |
| Tuesday | 2 | Incremental since Monday |
| Wednesday | 3 | Incremental since Tuesday |
| Thursday | 4 | Incremental since Wednesday |
| Friday | 5 | Incremental since Thursday |
| Saturday | 6 | Incremental since Friday |
Strategy: This approach minimizes storage requirements while allowing for point-in-time recovery.
Automating Backups
Automating your backup process ensures consistency and reduces the chance of human error.
Creating a Backup Script:
#!/bin/bash
# Variables
BACKUP_DIR="/backup"
DATE=$(date +%Y-%m-%d)
FILESYSTEM="/home"
# Create backup directory if it doesn't exist
mkdir -p $BACKUP_DIR
# Determine backup level
if [ ! -f $BACKUP_DIR/last_full_backup ]; then
LEVEL=0
echo $DATE > $BACKUP_DIR/last_full_backup
else
LAST_FULL=$(cat $BACKUP_DIR/last_full_backup)
DAYS_SINCE_FULL=$(( ( $(date -d "$DATE" +%s) - $(date -d "$LAST_FULL" +%s) ) / 86400 ))
if [ $DAYS_SINCE_FULL -ge 7 ]; then
LEVEL=0
echo $DATE > $BACKUP_DIR/last_full_backup
else
LEVEL=1
fi
fi
# Perform backup
dump -${LEVEL}uf $BACKUP_DIR/${FILESYSTEM##*/}-level${LEVEL}-${DATE}.dump $FILESYSTEM
Scheduling with Cron:
Add to crontab (crontab -e):
# Run backup daily at 2 AM
0 2 * * * /path/to/backup-script.sh
# Alternatively, directly in crontab
0 2 * * 0 dump -0uf /backup/home-full-$(date +\%Y-\%m-\%d).dump /home
0 2 * * 1-6 dump -1uf /backup/home-incr-$(date +\%Y-\%m-\%d).dump /home
Restoration Process
Proper restoration procedure is critical for recovering from data loss.
Restoring an Entire Filesystem:
- Boot from a live CD/USB if necessary
- Create and mount the target filesystem
- Change to the mount point directory
- Restore the full backup first
- Restore incremental backups in order
# Step 4: Restore full backup
restore -rf /backup/home-full.dump
# Step 5: Restore incremental backups in order
restore -rf /backup/home-incr1.dump
restore -rf /backup/home-incr2.dump
# ... continue for all incremental backups
Restoring Individual Files:
# List contents to find the file
restore -tf /backup/home-full.dump | grep filename
# Extract the specific file
restore -xf /backup/home-full.dump /path/to/filename
Warning: Practice restoration procedures regularly to ensure your backups are working correctly.
Best Practices
Follow these guidelines for a robust backup strategy.
General Guidelines:
- Test backups regularly with restoration drills
- Store backups offsite or on separate media
- Use encryption for sensitive data
- Monitor backup jobs for failures
- Keep multiple generations of backups
Dump-Specific Tips:
- Always use the -u flag to update /etc/dumpdates
- Regularly verify backups with restore -t
- Document your backup and restoration procedures
- Consider filesystem consistency (run fsck before backup if possible)
Remember: A backup is only as good as your ability to restore from it.
Example Backup Scripts
Here are some practical scripts for implementing a backup system.
Complete Backup Script:
#!/bin/bash
# Comprehensive backup script using dump
# Configuration
BACKUP_ROOT="/backup"
LOG_FILE="/var/log/backup.log"
FILESYSTEMS=("/home" "/var" "/etc")
RETENTION_DAYS=30
# Create backup directory with date
BACKUP_DATE=$(date +%Y-%m-%d)
BACKUP_DIR="$BACKUP_ROOT/$BACKUP_DATE"
mkdir -p "$BACKUP_DIR"
# Log function
log() {
echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" >> "$LOG_FILE"
}
log "Starting backup process"
# Check if dump is available
if ! command -v dump &> /dev/null; then
log "ERROR: dump command not found"
exit 1
fi
# Perform backup for each filesystem
for FS in "${FILESYSTEMS[@]}"; do
# Get filesystem name for backup file
FS_NAME=$(echo "$FS" | tr -d '/')
# Determine backup level
if [ ! -f "$BACKUP_ROOT/last_full_$FS_NAME" ]; then
LEVEL=0
echo "$BACKUP_DATE" > "$BACKUP_ROOT/last_full_$FS_NAME"
else
LAST_FULL=$(cat "$BACKUP_ROOT/last_full_$FS_NAME")
DAYS_SINCE_FULL=$(( ( $(date -d "$BACKUP_DATE" +%s) - $(date -d "$LAST_FULL" +%s) ) / 86400 ))
if [ $DAYS_SINCE_FULL -ge 7 ]; then
LEVEL=0
echo "$BACKUP_DATE" > "$BACKUP_ROOT/last_full_$FS_NAME"
else
LEVEL=1
fi
fi
# Create backup
BACKUP_FILE="$BACKUP_DIR/${FS_NAME}-level${LEVEL}.dump"
log "Backing up $FS to $BACKUP_FILE (level $LEVEL)"
if dump -${LEVEL}uf "$BACKUP_FILE" "$FS" 2>> "$LOG_FILE"; then
log "Successfully backed up $FS"
else
log "ERROR: Failed to back up $FS"
fi
done
# Clean up old backups
find "$BACKUP_ROOT" -type d -name "*-*-*" -mtime +$RETENTION_DAYS -exec rm -rf {} \; 2>/dev/null
log "Backup process completed"
Restoration Helper Script:
#!/bin/bash
# Interactive restoration script
echo "Available backups:"
find /backup -name "*.dump" | sort | nl
echo -n "Select backup to restore: "
read OPTION
BACKUP_FILE=$(find /backup -name "*.dump" | sort | sed -n "${OPTION}p")
if [ -z "$BACKUP_FILE" ]; then
echo "Invalid selection"
exit 1
fi
echo "Restoring from $BACKUP_FILE"
echo "Choose mode:"
echo "1) Interactive restore"
echo "2) Extract specific files"
echo "3) List contents"
echo -n "Select option: "
read MODE
case $MODE in
1)
restore -if "$BACKUP_FILE"
;;
2)
echo -n "Enter path to extract: "
read EXTRACT_PATH
restore -xf "$BACKUP_FILE" "$EXTRACT_PATH"
;;
3)
restore -tf "$BACKUP_FILE"
;;
*)
echo "Invalid option"
exit 1
;;
esac