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Man Pages


Manual Reference Pages  -  TARTARUS (1)

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NAME

tartarus - a flexible script based backup system

CONTENTS

SYNOPSIS

tartarus [--inc] profile

DESCRIPTION

Tartarus provides a nice wrapper around basic Unix tools such as tar, find and curl to provide a seamless backup solution. Instead of relying on single usage backup scripts or complicated command lines, tartarus reads its configuration from easily manageable configuration files. It can store gathered data in regular files, or upload the backup directly (on the fly) to an FTP server. For more specific usage scenarios, custom methods can also be defined within the config file.

OPTIONS AND ARGUMENTS

--inc | -i Override the INCREMENTAL_BACKUP configuration option and create an differential backup instead of a full one.
One additional argument is required to specify the profile file to load the backup configuration from.

CONFIGURATION

Tartarus reads it options from a configuration file specified at the command line. This file is in fact a shell script and has the duty of setting several variables that control the behaviour of the backup script. Each configuration file is called a profile.

Parameters can be set by a simple variable assignment or by using more complex methods for advanced use.

Whenever a boolean value is expected, the strings yes and no as well as 1 and 0 are accepted.
NAME The profile identifier used for archive files and various other purposes.
DIRECTORY The directory to be backed up; only a single directory name is allowed here.
STAY_IN_FILESYSTEM Enabling this directory will prevent the backup process from traversing into directories residing on different filesystems/partitions. This is especially useful when backing up the root directory /, since you probably do not want to store /proc or /sys.
CREATE_LVM_SNAPSHOT If this is set to yes, Tartarus will try to freeze the content of the LVM volume specified with LVM_VOLUME_NAME - The snapshot will then be mounted and used as the backup source.

Once set, the specification of LVM_VOLUME_NAME becomes mandatory.

LVM_VOLUME_NAME The LVM logical volume to take a snapshot from before backing up: Be sure to specify the correcet volume your DIRECTORY is on, otherwise weird things might happen.
SNAPSHOT_DIR Defaulting to /snap, a subdirectory with the name specified by LVM_MOUNT_DIR will be created in the specified directory to create a mount point for the snapshot volume. Afterwards, the SNAPSHOT_DIR becomes the new base directory for the backup process.
LVM_MOUNT_OPTIONS Additional options passed to the mount command
LVM_SNAPSHOT_SIZE This value specifies the amount of disk space reserved for the volume snapshot. It can handle any format the command lvcreate understands, e.g. 200m as well as 1G. Make sure your volume group has enough disk space to handle the growing divergence between the origin and the snapshot volume during the backup run. This value defaults to 200m.
ASSEMBLY_METHOD The method you would like to employ to combine your file system into an coherent data archive is defined by this variable. The default method is tar, but Tartarus also supports the more modern afio format. You must have the corresponding archive program installed.
TAR_OPTIONS This variable allows additional to be passed to tar. One common value would be --ignore-failed-read to ignore files that disappear during the backup run.
COMPRESSION_METHOD Tartarus can utilize various compression methods to the shrink the processed data before storing it. Leaving the variable blank (which is the default) will disable compression, other known values are gzip, bzip and pbzip.
STORAGE_METHOD This variable declares how the gathered and processed data should be stored. Various methods are included in Tartarus, while others can be added b custom configuration:
FILE Store the backup archives in the local file system
FTP Save the backup archives on-the-fly to an FTP server
SIMULATE Do not actually save any data, but send it directly to /dev/null
CUSTOM Using this storage method allows you to implement a custom storage method by defining a shell function called TARTARUS_CUSTOM_STORAGE_METHOD.
STORAGE_FILE_DIR When using local file storage, create backup archives in the directory specified by this variable.
STORAGE_FTP_SERVER
STORAGE_FTP_DIR
STORAGE_FTP_USER
STORAGE_FTP_PASSWORD Specify the FTP server backup data should be send to.
STORAGE_FTP_USE_SSL When enabled, this option forces an SSL-secured connection when transmitting data to the FTP server.
STORAGE_FTP_SSL_INSECURE Enabling this option makes Tartarus ignore certain security problems like self signed certificates.
STORAGE_FTP_USE_SFTP When enabled, tartarus uses SFTP instead of plain old FTP to access the server
STORAGE_CHUNK_SIZE The maximum file size (in MiB) the storage medium can handle. If this is set, the backup archive will be split in several files. It can be used to circumvent limitations in old FTP servers or file systems that cannot handle files larger than 2 GiB. To restore the data, the files have to be concatenated.
INCREMENTAL_BACKUP When set, Tartarus won’t create a full backup but only save files that have been modified after the file set by INCREMENTAL_TIMESTAMP_FILE has been touched. Instead of enabling this option in the configuration file, this option can be set by specifying the parameter --inc on the command line.
INCREMENTAL_TIMESTAMP_FILE Everytime a full backup is successfully completed, Tartarus will touch the file specified here as a reference point for future incremental backups.
INCREMENTAL_STACKING With this option enabled, Tartarus will also update the flagfile after completing a successfull partial (differential/incremental) backup run. By that, incremental backups are stacked on each other instead of being based on the most recent full backup.
EXCLUDE Directories that should be excluded from the backup can be placed in this variable. While Tartarus will not traverse into these directories, they will be included in the backup, although without their content.
EXCLUDE_FILES Files from directories specified in this list will not be included in the backups, while any subdirectories beneath them will be saved, discarding the actual file content but preserving the directory structure.
EXCLUDE_FILENAME_PATTERNS This variable holds a list of filename patterns to be excluded from the backup.
ENCRYPT_SYMMETRICALLY When enabled, this option makes Tartarus encrypt the backup archive using a password read from the file ENCRYPT_PASSPHRASE_FILE.
ENCRYPT_PASSPHRASE_FILE The file specified in this variable stores the passphrase used to encrypt the backup data. Losing the passphrase most certainly leads to a complete loss of the backup data, so it should be stored at a safe place.
ENCRYPT_ASYMMETRICALLY If enabled, the backup data will be encrypted using the public key specified by ENCRYPT_KEY_ID. If both ENCRYPT_SYMMETRICALLY and ENCRYPT_ASYMMETRICALLY are enabled, decryption will be possible with the private key or the supplied passphrase (one of them will be sufficient).
ENCRYPT_KEY_ID This option defines the key id to be used by GnuPG to encrypt the data.
ENCRYPT_KEYRING This variable points to the location of the keyring handed to GnuGP.
ENCRYPT_GPG_OPTIONS Any additional options can be passed to GnuPG by editing this variable.
LIMIT_DISK_IO When enabled, the input/output load of the backup process will be limited using using the ionice utility.
CHECK_FOR_UPDATE Disabling this option will stop Tartarus from checking its website for updates of itself.
FILE_LIST_CREATION Enabling this option causes Tartarus to write a list of all processed files to the location specified by FILE_LIST_DIRECTORY.
FILE_LIST_DIRECTORY This defines the directory lists of the processed files are placed in.
SFTP_AUTH_METHOD Defines SFTP authentication method: can be password or pubkey
SFTP_AUTH_PRIVKEY Defines SSH private key for authentication
SFTP_AUTH_PUBKEY Defines SSH public key for authentication
SFTP_AUTH_PRIVKEY_TYPE Defines SSH private key type (PEM|DER|ENG)A Defaults to PEM
SFTP_AUTH_PRIVKEY_PASS Defines SFTP_AUTH_PRIVKEY passphrase
SFTP_AUTH_HOSTPUBMD5 Defines SFTP host MD5 pubkey

EXAMPLE

    Basic configuration

Suppose you want to backup your home directories on a regular basis; the compressed archive will be stored on a FTP server. This can be achieved easily with just a few lines of tartarus configuration. Let’s call the profile definition /etc/tartarus/homedirs.conf:



    # Thats the profile name
    NAME="homedirs"
    DIRECTORY="/home"
    # We store it using FTP, on the fly
    STORAGE_METHOD="FTP"
    STORAGE_FTP_SERVER="ftpbackup.hostingcompany.com"
    STORAGE_FTP_USER="johndoe"
    STORAGE_FTP_PASSWORD="verysecret"
    COMPRESSION_METHOD="bzip2"



By calling tartarus /etc/tartarus/homedirs.conf the script will gather all files below /home, compress them using bzip2 and store it on the FTP server ftpbackup.hostingcompany.com.

    LVM snapshots

Backing up a partition that is in use can lead to inconsistent backups. To avoid this, Tartarus supports the use of LVM snapshots to freeze the block device and operate on that static copy. The real volume can still be used while changes done to the file system structure are not reflected on the frozen block device.

To use this feature, the file system you wish to back up has to reside on an LVM volume and the volume group has to have some free space to store the differences between snapshot and real volume that accumulate during the backup run. You also have to make sure that the directory /snap does exist, since tartarus mounts the created snapshot volume below that directory.

A few additional lines instruct Tartarus to use the snapshot functionality:



    # Users keep on working
    CREATE_LVM_SNAPSHOT="yes"
    LVM_VOLUME_NAME="/dev/volumegroup0/home"
    LVM_MOUNT_DIR="/home"
    # Allocate enough space for any changes during the backup run
    LVM_SNAPSHOT_SIZE="1000m"



    Incremental backups

Storing a full backup takes a lot of disk space; Often just storing the files that changed since the last backup is more desirable - this is called a incremental backup.

Tartarus can create a flag file on your system that is used as a reference point when doing the next incremental backup. To do this, just add the following line to your config:



    INCREMENTAL_TIMESTAMP_FILE="/var/spool/tartarus/homedirs"



Everytime a full backup run succeeds, this file is touched by Tartarus.

To create an incremental backup based on that file, just add these lines to a profile:



    INCREMENTAL_BACKUP="yes"
    INCREMENTAL_TIMESTAMP_FILE="/var/spool/tartarus/homedirs"



Instead of copying the profile file and adding the lines, you can also just reuse the existing configuration profile and start Tartarus with the option -i: ’tartarus -i /etc/tartarus/homedirs.conf’ will create an incremental backups based on the latest flag file deposited by the last full run.

As already said, incremental backups are (normally) based on the last full backup; usually, this is called a differential backup:



    [F1]->[D1]           [F2]->[D4]
        \----->[D2]         \------>[D5]
         `--------->[D3]     `---------->[D6]



While this backup strategy simplifies recovery (since only the most recent full and the most recent differential archive has to be extracted, e.g. F2 and D6), it can waste backup space in some cases. If a large file is added to the system after the full backup has been created, this file will appear in every partial backup afterwards.

Another strategy is a real incremental backup, which is called a stacked incremental backup in Tartarus terminology. Instead of basing the partial backup on the last full run, it is based on the last successfull run - be it complete or partial as well.



    [F1]->[I1]->[I2]->[I3]
                          [F2]->[I4]->[I5]->[I6]



This behaviour will save space, since new (and unchanged) files will only appear in one archive. However, restoring a filesystem will require all archives to be extracted (F2 _and_ I4 _and_ I5 _and_ _I5_)

Setting INCREMENTAL_STACKING to yes will enable this behaviour and makes Tartarus update the timestamp file after every backup run, not only after full backups.

    Encryption

Tartarus supports symmetric encryption through gpg (GNU Privacy Guard). To utilize it, write your passphrase into a file, for example /etc/tartarus/backups.sec, and place it at a safe location: You might need it one day to restore your precious backup data. Now tell Tartarus where to find the secret passphrase by adding the following lines to your profile:



    ENCRYPT_SYMMETRICALLY="yes"
    ENCRYPT_PASSPHRASE_FILE="/etc/tartarus/backups.sec"



Also make sure that the passphrase file is only readable by root; otherwise anyone with access to that file can decrypt your backups.

Asymmetric encryption is also possible. Just specify a key id to encrypt the backup archive using that public key:



    ENCRYPT_ASYMMETRICALLY="yes"
    ENCRYPT_KEY_ID="ABC12345"



The resulting backup profile can only be decrypted using the matching private key.

Symmetric and asymmetric encryption can also be combined: Then one credential, either the private key or the passphrase, is sufficient to decrypt the backup archive.

Restoring a backup

Even more important than creating a backup is restoring it. Since Tartarus is largely based on standard unix tools, you won’t have to install special software - even a basic rescue system will suffice to retrieve your lost data.

Given that the backup is stored on an FTP server, compressed an encrypted, we need the following tools to restore it:
o curl, wget or any other FTP client
o gpg to decrypt the backup stream
o gzip or bzip, depending on the compression method used
o tar to extract the archive
o afio (or cpio) to extract the archive when using this file format
This enumeration is also the order in which to apply these programs; First download the tar archive to your system, then use gpg --decrypt to, well, decrypt it. After that you can expand the file by using gzip -d (or the equivalent of bzip2) and retrieve the naked tar archive, which can then be manipulated by the usual tar commands.

If you do not have enough disk space to store the entire backup, you can also restore it on the fly; just use the pipe feature of any unix shell:



    $ curl ftp://USER:PASS@YOURSERVER/home-20080411-1349.tar.bz2.gpg \
        | gpg --decrypt \
        | bzip2 -d \
        | tar tpv



The tar command tpv prints the archives content while using numeric UID/GID values for files (so it won’t change file ownership while in the rescue system). If you really want to extract the archive, replace t with an x (eXtract).

If you are using the afio file format, compression does not take part on the entire stream, but is handled by afio itself on a per file basis. The command line for listing such a backup might look like this:



    $ curl ftp://USER:PASS@YOURSERVER/home-20080411-1349.tar.bz2.gpg \
        | gpg --decrypt \
        | afio -Z -P bzip2 -t -



To restore incremental backups, just restore the last full backup as well as the most recent incremental one.

Defining a custom storage method

Tartarus supports the creation of custom storage methods. No changes to the program are necessary to achieve this: Simply set the storage method in the configuration file to CUSTOM:

STORAGE_METHOD=CUSTOM

Then define a shell function with the name TARTARUS_CUSTOM_STORAGE_METHOD. The method should read the backup data from STDIN, while the proposed archive filename is stored in the shell variable $FILENAME. The following example uses the secure shell to transmit the archive to a remote location:



    TARTARUS_CUSTOM_STORAGE_METHOD() {
        local USER="stefan"
        local HOST="zirkel.wertarbyte.de"
        debug "Sending backup to $USER@$HOST:~/$FILENAME through SSH..."
        ssh $USER@$HOST "cat > ~/$FILENAME"
    }



Any exit code except 0 is considered an error and will abort the backup process. If the archive is to be split into multiple chunks, the storage method might be called more than once.

Tartarus processing hooks

For special configuration purposes, the Tartarus scripts offers special hooks where user supplied code can be placed and executed during the backup procedure.

The following hooks are called during the run of the program:
TARTARUS_PRE_PROCESS_HOOK


    Called right after the config file has been read and the program starts



TARTARUS_POST_PROCESS_HOOK


    Called right before the program terminates gracefully, before the cleanup
    procedure



TARTARUS_PRE_CONFIGVERIFY_HOOK


    Called before the configuration gets verified (after TARTARUS_PRE_PROCESS_HOOK)



TARTARUS_POST_CONFIGVERIFY_HOOK


    Called after all configuration options and command line arguments have been inspected



TARTARUS_PRE_CLEANUP_HOOK


    Called before the cleanup procedure runs, the variable ABORT indicates whether
    the program terminated gracefully



TARTARUS_POST_CLEANUP_HOOK


    Called at the end of the cleanup procedure



TARTARUS_PRE_FREEZE_HOOK


    Called right before a LVM snapshot is created



TARTARUS_POST_FREEZE_HOOK


    Called right after a LVM snapshot has been created



TARTARUS_PRE_STORE_HOOK


    Called right before the backup data is gathered and stored



TARTARUS_POST_STORE_HOOK


    Called right after the backup has been stored



TARTARUS_DEBUG_HOOK


    Called whenever a debug message (contained in the variable DEBUGMSG) is printed



Each segment of the backup procedure - gathering , bundling, compression, encryption and storage - itself is also embraced by a pair of hooks. Those functions however are integrated into the pipeline that transports your backup data, so writing to STDOUT or reading from STDIN in a hook might destroy your data. Only do so if you know exactly what you are doing.
TARTARUS_PRE_FIND_HOOK / TARTARUS_POST_FIND_HOOK


    Executed before/after the find process gathers the files to be saved



TARTARUS_PRE_TAR_HOOK / TARTARUS_POST_FIND_HOOK


    Executed before/after tar bundles the files to an archive stream



TARTARUS_PRE_COMPRESSION_HOOK / TARTARUS_POST_COMPRESSION_HOOK


    Executed before/after the data stream is handled by the compression software



TARTARUS_PRE_COMPRESSION_HOOK / TARTARUS_POST_COMPRESSION_HOOK


    Executed before/after the data stream is processed by the encryption software



TARTARUS_PRE_STORAGE_HOOK / TARTARUS_POST_STORAGE_HOOK


    Executed before/after the stream is handed over to the storage function



To use a hook, define a shell function of the name in your config file.

As an example, this hook function transfers all debug messages to your syslog system:



    TARTARUS_DEBUG_HOOK() {
        echo $DEBUGMSG | logger
    }



Hooks can also increase the reliability of the snapshot functionality. LVM snapshots can lead to slightly inconsistent file systems, since they do not freeze the file system, but the underlying block device. This is why Tartarus calls ’sync’ right before creating the snapshot volume. Most filesystems can cope with that issue. But if you want to make sure that the snapshot file system is valid, hooks can be used to run a file system check on the snapshot volume before mounting it:



    TARTARUS_PRE_FREEZE_HOOK() {
        # make sure everything is synced to disk
        # before snapshotting
        sync
    }

    TARTARUS_POST_FREEZE_HOOK() {
        # we can access the internal variables
        # of the tartarus process, but take care!
        #
        # $SNAPDEV should contain the volume we are
        # about to mount, try auto-repair
        /sbin/fsck -y "$SNAPDEV"
    }



AUTHOR

Stefan Tomanek <stefan.tomanek+tartarus@wertarbyte.de> http://wertarbyte.de/tartarus.shtml
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0.9.8 TARTARUS (1) 2016-04-03

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