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When you add a fresh USB DRIVE to Linux, it should automatically assign it a device. Something like:

• /dev/sda
• /dev/sdb
• /dev/sdc
• /dev/sdd

and so on.

Discover the USB Drive

The easiest way to check this is to look through the message log::

grep kernel /var/log/messages

You will see something like:

Sep 26 18:07:24 server kernel: usb 2-1: new high speed USB device using ehci_hcd and address 5
Sep 26 18:07:24 server kernel: usb 2-1: configuration #1 chosen from 1 choice
Sep 26 18:07:24 server kernel: scsi6 : SCSI emulation for USB Mass Storage devices
Sep 26 18:07:24 server kernel: usb-storage: device found at 5
Sep 26 18:07:24 server kernel: usb-storage: waiting for device to settle before scanning
Sep 26 18:07:29 server kernel:   Vendor: ST310003  Model: 40AS              Rev:
Sep 26 18:07:29 server kernel:   Type:   Direct-Access                      ANSI SCSI revision: 02
Sep 26 18:07:30 server kernel: SCSI device sdd: 1953523055 512-byte hdwr sectors (1000204 MB)
Sep 26 18:07:30 server kernel: sdd: Write Protect is off
Sep 26 18:07:30 server kernel: sdd: Mode Sense: 34 00 00 00
Sep 26 18:07:30 server kernel: sdd: assuming drive cache: write through
Sep 26 18:07:30 server kernel: SCSI device sdd: 1953523055 512-byte hdwr sectors (1000204 MB)
Sep 26 18:07:30 server kernel: sdd: Write Protect is off
Sep 26 18:07:30 server kernel: sdd: Mode Sense: 34 00 00 00
Sep 26 18:07:30 server kernel: sdd: assuming drive cache: write through
Sep 26 18:07:30 server kernel:  sdd:
Sep 26 18:07:30 server kernel: sd 6:0:0:0: Attached scsi disk sdd
Sep 26 18:07:30 server kernel: sd 6:0:0:0: Attached scsi generic sg3 type 0
Sep 26 18:07:30 server kernel: usb-storage: device scan complete

If you look closely at the above logs, you will see that the system assigned the letter d to the USB DRIVE. So, the device is /dev/sdd

If the USB DRIVE already has a file system on it, you might be able to find more details by:

df -h

or simply

mount

Partition the USB DRIVE

The fresh USB DRIVE will have no filesystem so it probably won't be mounted anywhere. To format the USB DRIVE:

• fdisk /dev/sdd
• n (to add a new partition)
• p (to make a primary partition)
• 1 (that's the number one, the number you want to assign to the partition)
• w (write and exit)

Format the USB DRIVE

Now that there is a partition on the USB DRIVE, we have to format the partition with a filesystem.

• mkfs.ext3 -L BackupDrive1 /dev/sdd1

Where

• ext3 is the filesystem itself (explaining filesystems is beyond this article).
• -L option is to label the USB DRIVE

Mount the USB DRIVE

To mount the USB DRIVE, issue a:

• mount /dev/sdc1 /media/BackupDrive1/

Reliably mount multiple disks in the one location

In case you want to use a rotating set of disk drives for backups, you may want to mount different USB DRIVES in the same location. Of course, make sure you don't plug both in at the same time.

Edit the /etc/fstab. Add the lines by typing:

• LABEL=BackupDrive1      /media/BackupDrive1     ext3    defaults
• LABEL=BackupDrive2      /media/BackupDrive1     ext3    defaults

Set The Label On The Partition

This will set the label on the partition:

• e2label /dev/sdd1 MyLabel

Check The Label On The Partition

This will check the label on the partition:

• e2label /dev/sdd1

Unmount the USB DRIVE

If you need to unmount the USB DRIVE, it's like this:

• umount /media/BackupDrive1/

How to Keep the USB DRIVE From Falling Asleep

I won't go into too much detail here but sometimes the USB DRIVE is going to fall asleep because of the USB DRIVE CADDY that it is in. The easist way for me to fix it was to mount it around 5 minutes before the back is scheduled to start.

• mkdir -p /etc/e-smith/templates-custom/etc/crontab/26usb-drive
• vi 26usb-drive

# Keep the USB drive from going into standby.
#5 * * * * /bin/touch /dev/sdc &>/dev/null
50 21 * * * root mount /dev/sdc1 /media/BackupDrive1/
55 21 * * * root umount /media/BackupDrive1/

How to Selective Restore From DAR Backup

Here's how to selective restore from DAR backup:

dar -x /media/BackupDrive1/server.domain.local/set2/full-201408092200 -N -R / -w -g home/e-smith/files/ibays/share_data/files

You will also have to restore all the incrementals:

dar -x /media/BackupDrive1/server.domain.local/set2/inc-001-201408102200.1.dar -N -R / -w -g home/e-smith/files/ibays/share_data/files
dar -x /media/BackupDrive1/server.domain.local/set2/inc-002-201408112200.1.dar -N -R / -w -g home/e-smith/files/ibays/share_data/files
dar -x /media/BackupDrive1/server.domain.local/set2/inc-003-201408122200.1.dar -N -R / -w -g home/e-smith/files/ibays/share_data/files
dar -x /media/BackupDrive1/server.domain.local/set2/inc-004-201408132200.1.dar -N -R / -w -g home/e-smith/files/ibays/share_data/files

How to Manually Start a Backup

Here's how to manually start a backup routine

• /sbin/e-smith/do_backupwk

How to Set the Backup Sets

Backup Sets are an entire week; a full backup on Friday plus the remaining 6 days (SAT, SUN, MON, TUE, WED, THU). This data can be large. Currently, on one server, I have 600GB of data for the entire backup set.

A USB backup drive needs to be large enough for the number of full sets you want (how far back in history do you want to go) + 1. In other words, N + 1.

As an example, if you have a 2TB drive and you can only go back 2 sets.

Why? Well if you have 3 sets that is a total of 1.8TB (600 x 3) which is the desired result. The problem becomes that the next backup cannot run because it collects the backup and then it deletes the oldest backup. The next backup can only go to about 200GB and then it will error out. I learned this the hard way.

Putting the backup sets to 2 will result in 1.2TB. The next backup set will finish for a total of 1.8TB and then delete the oldest backup for a total of 1.2TB again.