Setting up a Pool of One
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## Setting up a Pool of One

Cedar Backup has been designed primarily for situations where there is a single master and a set of other clients that the master interacts with. However, it will just as easily work for a single machine (a backup pool of one).

Once you complete all of these configuration steps, your backups will run as scheduled out of cron. Any errors that occur will be reported in daily emails to your root user (or the user that receives root's email). If you don't receive any emails, then you know your backup worked.

Note: all of these configuration steps should be run as the root user, unless otherwise indicated.

### Tip

This setup procedure discusses how to set up Cedar Backup in the “normal case” for a pool of one. If you would like to modify the way Cedar Backup works (for instance, by ignoring the store stage and just letting your backup sit in a staging directory), you can do that. You'll just have to modify the procedure below based on information in the remainder of the manual.

### Step 1: Decide when you will run your backup.

There are four parts to a Cedar Backup run: collect, stage, store and purge. The usual way of setting off these steps is through a set of cron jobs. Although you won't create your cron jobs just yet, you should decide now when you will run your backup so you are prepared for later.

Backing up large directories and creating ISO filesystem images can be intensive operations, and could slow your computer down significantly. Choose a backup time that will not interfere with normal use of your computer. Usually, you will want the backup to occur every day, but it is possible to configure cron to execute the backup only one day per week, three days per week, etc.

### Warning

Because of the way Cedar Backup works, you must ensure that your backup always runs on the first day of your configured week. This is because Cedar Backup will only clear incremental backup information and re-initialize your media when running on the first day of the week. If you skip running Cedar Backup on the first day of the week, your backups will likely be “confused” until the next week begins, or until you re-run the backup using the `--full` flag.

### Step 2: Make sure email works.

Cedar Backup relies on email for problem notification. This notification works through the magic of cron. Cron will email any output from each job it executes to the user associated with the job. Since by default Cedar Backup only writes output to the terminal if errors occur, this ensures that notification emails will only be sent out if errors occur.

In order to receive problem notifications, you must make sure that email works for the user which is running the Cedar Backup cron jobs (typically root). Refer to your distribution's documentation for information on how to configure email on your system. Note that you may prefer to configure root's email to forward to some other user, so you do not need to check the root user's mail in order to see Cedar Backup errors.

### Step 3: Configure your writer device.

Before using Cedar Backup, your writer device must be properly configured. If you have configured your CD/DVD writer hardware to work through the normal filesystem device path, then you just need to know the path to the device on disk (something like `/dev/cdrw`). Cedar Backup will use the this device path both when talking to a command like cdrecord and when doing filesystem operations like running media validation.

Your other option is to configure your CD writer hardware like a SCSI device (either because it is a SCSI device or because you are using some sort of interface that makes it look like one). In this case, Cedar Backup will use the SCSI id when talking to cdrecord and the device path when running filesystem operations.

See the section called “Configuring your Writer Device” for more information on writer devices and how they are configured.

### Note

There is no need to set up your CD/DVD device if you have decided not to execute the store action.

Due to the underlying utilities that Cedar Backup uses, the SCSI id may only be used for CD writers, not DVD writers.

### Step 4: Configure your backup user.

Choose a user to be used for backups. Some platforms may come with a “ready made” backup user. For other platforms, you may have to create a user yourself. You may choose any id you like, but a descriptive name such as `backup` or `cback` is a good choice. See your distribution's documentation for information on how to add a user.

### Note

Standard Debian systems come with a user named `backup`. You may choose to stay with this user or create another one.

### Step 5: Create your backup tree.

Cedar Backup requires a backup directory tree on disk. This directory tree must be roughly three times as big as the amount of data that will be backed up on a nightly basis, to allow for the data to be collected, staged, and then placed into an ISO filesystem image on disk. (This is one disadvantage to using Cedar Backup in single-machine pools, but in this day of really large hard drives, it might not be an issue.) Note that if you elect not to purge the staging directory every night, you will need even more space.

You should create a collect directory, a staging directory and a working (temporary) directory. One recommended layout is this:

    /opt/
         backup/
                collect/
                stage/
                tmp/

If you will be backing up sensitive information (i.e. password files), it is recommended that these directories be owned by the backup user (whatever you named it), with permissions `700`.

### Note

You don't have to use `/opt` as the root of your directory structure. Use anything you would like. I use `/opt` because it is my “dumping ground” for filesystems that Debian does not manage.

Some users have requested that the Debian packages set up a more “standard” location for backups right out-of-the-box. I have resisted doing this because it's difficult to choose an appropriate backup location from within the package. If you would prefer, you can create the backup directory structure within some existing Debian directory such as `/var/backups` or `/var/tmp`.

### Step 6: Create the Cedar Backup configuration file.

Following the instructions in the section called “Configuration File Format” (above) create a configuration file for your machine. Since you are working with a pool of one, you must configure all four action-specific sections: collect, stage, store and purge.

The usual location for the Cedar Backup config file is `/etc/cback.conf`. If you change the location, make sure you edit your cronjobs (below) to point the cback script at the correct config file (using the `--config` option).

### Warning

Configuration files should always be writable only by root (or by the file owner, if the owner is not root).

If you intend to place confidential information into the Cedar Backup configuration file, make sure that you set the filesystem permissions on the file appropriately. For instance, if you configure any extensions that require passwords or other similar information, you should make the file readable only to root or to the file owner (if the owner is not root).

### Step 7: Validate the Cedar Backup configuration file.

Use the command cback validate to validate your configuration file. This command checks that the configuration file can be found and parsed, and also checks for typical configuration problems, such as invalid CD/DVD device entries.

Note: the most common cause of configuration problems is in not closing XML tags properly. Any XML tag that is “opened” must be “closed” appropriately.

### Step 8: Test your backup.

Place a valid CD/DVD disc in your drive, and then use the command cback --full all. You should execute this command as root. If the command completes with no output, then the backup was run successfully.

Just to be sure that everything worked properly, check the logfile (`/var/log/cback.log`) for errors and also mount the CD/DVD disc to be sure it can be read.

If Cedar Backup ever completes “normally” but the disc that is created is not usable, please report this as a bug. [20] To be safe, always enable the consistency check option in the store configuration section.

### Step 9: Modify the backup cron jobs.

Since Cedar Backup should be run as root, one way to configure the cron job is to add a line like this to your `/etc/crontab` file:

    30 00 * * * root  cback all

Or, you can create an executable script containing just these lines and place that file in the `/etc/cron.daily` directory:

    #/bin/sh
    cback all

You should consider adding the `--output` or `-O` switch to your cback command-line in cron. This will result in larger logs, but could help diagnose problems when commands like cdrecord or mkisofs fail mysteriously.

### Note

For general information about using cron, see the manpage for crontab(5).

On a Debian system, execution of daily backups is controlled by the file `/etc/cron.d/cedar-backup2`. As installed, this file contains several different settings, all commented out. Uncomment the “Single machine (pool of one)” entry in the file, and change the line so that the backup goes off when you want it to.

[20] See https://bitbucket.org/cedarsolutions/cedar-backup2/issues.

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