 The
smbbackup Utility
Sandor Patocs
Although Linux has enjoyed tremendous growth and increased popularity,
many organizations still heavily favor the use of Windows. CostWare,
the company I work for, provides a cost recovery system for professional
organizations such as law firms. It is not uncommon for CostWare
to be the only Linux-based application server in a firm.
For larger firms, the task of backing up a Linux system is not
a problem. However, for smaller firms with small or non-existent
IT departments, this can be a daunting task. The backup software
used by smaller organizations often does not provide a backup solution
for Linux. In cases like this, CostWare uses a utility called smbbackup
to back up the CostWare server to a shared Windows drive. This allows
the firm to use its existing Windows-based backup software to archive
critical files. One advantage to using this utility is that the
Linux system does not need to join the Active Directory domain to
back up files to the Windows server.
The smbbackup utility was originally designed to provide a means
of backing up Linux systems. It can also be used to back up any
other Unix-based system that has a minimal Samba installation in
place. smbbackup uses tools that are part of the Samba suite to
back up Unix files to a SMB/CIFS (Windows) share. The program uses
the smbclient program to perform the actual operations needed to
transfer files and directories. Directories and their contents,
including sub-directories, are copied to the remote server. Entire
directory trees are copied by default. The utility's include/exclude
options may be used to include or exclude specific files and directories.
Installation
Installation of the utility is straightforward. Simply download
the tar file from http://www.costwareinc.com/freesoftware/.
The utility is packaged as a self-extracting executable. Simply
run the installer as root and answer a few questions.
The following is a sample installation session:
$./smbbkup.installer
Installation directory [/usr/local/sbin]:
Installng SmbclientParser ... OK
Installing smbbackup utility ... OK
Installation complete
Command-Line Options
The smbbackup utility reads options from the command line or from
a file using the "directions" option (direction files will be discussed
later):
-a /root/authfile, -auth /root/authfile
This option allows you to specify a file from which to read the username,
domain name, and password used in the connection. The format of the
file is:
username = <value>
password = <value>
domain = <value>
If the domain parameter is missing, then the current workgroup name
is used instead. Be sure that the permissions on the file restrict
access from unwanted users:
-c, -clean -- New files and directories are copied to the location
specified using the --to option. Existing files and directories
on the destination server are not removed by default. This means
that the "to" location will continue to grow as new files and directories
are copied to it. This option causes a remote file or directory
to be removed before a new copy is transferred. Directories are
removed in their entirety, including sub-directories. Existing files
are overwritten when this option is not used.
-d directions, -directions directions -- Instead of specifying
options on the command line, all options can be saved in a "directions"
file. The options in the file are stored as key/value pairs. The
"key" is the name of a command-line option with the leading hyphen(s)
optionally removed. The "values" are the same as those used on the
command line (see File 1 below):
clean = 1
include = /
exclude = /proc
exclude = /dev
make = 1
auth = /etc/smbbackup/nt_auth
File 1 -- Sample Directions File
-e pattern, -exclude pattern -- Files and directories that
match "pattern" are not transferred. The pattern may be a regular
expression.
-f back_this_up, -from back_this_up -- The file or directory
to be backed up. If a directory is specified, all of its sub-directories
are backed up by default. Use the --exclude option to exclude
sub-directories. Use a combination of a directory name and an --include
pattern to select multiple files for backup.
-i pattern, -include pattern -- Only files and directories
that match the given pattern are transferred. The pattern may be
a regular expression. "Exclude" directives override "include" directives.
You can select multiple files using a wildcard with the --include
option and then selectively filter out individual items using --exclude.
-l logfile, -log logfile -- The "logfile" contains a list
of all of the files transferred as well as any error messages from
the smbclient program.
-p password, -password password -- The "password" for the
username used to log in to the remote server. This option is passed
to the smbclient program.
-t to_here, -to to_here -- "To_here" is the service name
of the remote SMB/CIFS share. The value is in the form //host/share/subfolder
where "host" is the name of the remote server and "share" is the
share name. This "//host/share" portion of this option is passed
to the smbclient program. The subfolder section causes smbackup
to backup files to the subfolder indicated, which means that a single
share can be used to provide access to multiple backup subfolders.
-u username, -user username -- The username used to log
in to the remote server. This option is passed to the smbclient
program.
Directions Files
The "directions" option can be used to store backup directions
in a file. The options used in the file are the same as those available
on the command line. Direction files can be chained together, which
is helpful when attempting to put together a complex backup system.
The samples shown in Listings 1-6 are fairly simplistic and reflect
how smbbackup can be configured to perform a full and a partial
backup for a Linux and Mac OS X system. The name of the full backup
file (Listing 1) is passed to the smbackup utility to perform a
full backup. The name of the partial backup file (Listing 2) is
used when performing a partial backup. Note that the partial backup
file relies on the local include files (Listings 4 and 6) to limit
the files that are actually backed up. In both cases, user home
directories and local application directories are backed up.
The Linux exclude file (Listing 3) excludes items such as /dev
and /proc. With these directories excluded, it is safe to use the
full backup file (Listing 1) on either the Linux or Mac system.
Also note the date specification in the to directive (see
Listings 1 and 2). This means that new backup destination folder
names that include the date and time can be generated automatically.
The make directive must be used whenever the date is to be
embedded into a destination folder's name.
The one-letter variables that begin with a % are expanded
using the strftime function. These date conversion specifications
are the same as those used by the date command available
on most Unix-like systems. See the man page for date or strftime
for a complete list of available variables.
Examples
The use of files containing directions is ideal for someone wanting
to put together a complete backup system. However, sometimes a quick
backup of a local directory or system is all that's needed. Below
are a few simple examples that can be run from the command line
or from "cron".
To copy all of the files in the Unix directory /home/foobar to
the share //server/share:
smbbackup --from /home/foobar --to //server/share --username
Administrator --password password
To copy the files in the Unix directory /home/foobar to the share
//server/share, while excluding core files:
smbbackup --from /home/foobar --to //server/share --exclude core
--username Administrator --password password
To copy all files to the share //server/share (this excludes device
files, the /proc filesystem, and /tmp):
smbbackup --from / --to //server/share --exclude /dev
--exclude /proc --exclude /tmp --username Administrator --password
password
Restoring Files
Restoring files is accomplished using the smbrestore utility.
The command-line options used with smbrestore are virtually the
same as those used with smbbackup. The main difference is that the
meanings of the from and to options are reversed.
The from option is used to refer to a remote Windows share,
and to refers to a local directory.
smbrestore accepts the following options:
-a, -auth
-f, -from
-t, -to
-u, -username
-p, -password
-d, -directions
Shortcomings
The smbbackup utility cannot back up special files such as character
or block device files, named pipes, and so on. There is no way to
make such files on a Windows system. Smbbackup is best suited for
backing up regular files and directories that may need to be restored
to an already running system. It should not be relied upon for bare-metal
restores.
Conclusion
The smbbackup utility provides an easy to use command-line interface
for backing up files to an SMB/CIFS share. Through the use of direction
files, a systems administrator can configure a fairly complete backup
scheme. The utility does not back up device files or other types
of special files, so it is not a good tool for a bare-metal recovery.
However, when a simple backup of user files and applications is
needed, it can be very useful.
Sandor Patocs is a paralegal and a Microsoft Certified Systems
Engineer. He has been working as a technical writer, programmer,
and administrator of various flavors of Unix for more than 10 years.
He works as a senior developer for CostWare, Inc. in Los Angeles.
He can be contacted at: sandorpatocs@netscape.net. | 
