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Backup with dump

May 15, 2009

dump is a rather aged, but still very useful Unix tool for backuping ext2 and ext3 filesystems. I use it for complete backup of my home partition, which is useful to restore it completely after a disk crash, stolen laptop etc.

For those who don't want to read the whole manpage to grasp how to basically call dump, a short explanation:

dump -3u -h 0 -f - /home | gzip > /path/to/backup/directory/backupfile.dump.gz

The first number, 3 here, is the dump level used for incremental backup - you need to increase it every time if you only want to do incremental backups (which I do daily); the appended -u means "update the list of backups". The -h 0 option tells dump to "honor the nodump flag", meaning that files marked with the attribute "nodump" will not be backuped at dump levels at or above 0 (hence, they are never backuped - I use this flag for videos, pretty pictures and other files I don't need essentially). See later for the dump flag.

The -f - tells dump where to store the backup file, which in this case is the standard output (-). The final parameter is the file system (device or mount point) which will be backuped.

I let dump output to the standard output, which I pipe into gzip to get the backup file a bit smaller. I use an NFS mount point for the target backup file, which means the file is stored on my server. You could, of course, give a filename after -f, and omit the piping to gzip.

nodump flag

This is an ext2/3 filesystem attribute, which is used by dump (when you tell it to) to determine whether a file or directory needs to be backuped at all. I use this to flag files and folders that are not essentially needed, but are rather large, like videos or picture folders. The attribute is set with:

chattr +d <file or directory>

You can also clear the attribute with the same command using -d. You can also view ext2/3 attributes with:

lsattr

The syntax of the lsattr command is quite similar to the syntax of the well-known ls command.

Shell script

You should do a full backup every so often, otherwise you will need ALL backup files to restore completely. You will also need to do a full backup before being able to backup incrementally. You can do a full backup with -0u (use the full argument to the script).

Below I present a small shell script I use for daily incremental backup. The basic idea is to count the backup number automatically, and to create backup files with the backup date appended to a prefix. Use the script at your own regard:

#!/bin/bash # LAST_BACKUP="/etc/last_backup" BACKUP_PATH="/mnt/public/David/_bak/laptop" BACKUP_MOUNTPOINT="/home" sudo smbmount //LINUX/PUBLIC /mnt/public sudo umount "$BACKUP_MOUNTPOINT" if [ "$1" = "full" ]; then if sudo dump -0 -u -h 0 -f - /home | gzip > "$BACKUP_PATH/home-full-`date +%Y-%m-%d`.dump.gz"; then echo 0 | sudo tee "$LAST_BACKUP" > /dev/null exit 0 fi exit 1 fi lb=`cat "$LAST_BACKUP"` nb=`expr $lb + 1` if sudo dump -$nb -u -h 0 -f - /home | gzip > "$BACKUP_PATH/home-`date +%Y-%m-%d`.dump.gz"; then echo $nb | sudo tee "$LAST_BACKUP" > /dev/null fi sudo mount "$BACKUP_MOUNTPOINT"

Last modified: September 07, 2009

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