System Administration Guide: Basic Administration

Chapter 50 UFS Backup and Restore Commands (Reference)

This chapter contains reference information on the ufsdump and ufsrestore commands.

This is a list of information in this chapter.

How the ufsdump Command Works

The ufsdump command makes two passes when it backs up a file system. On the first pass, this command scans the raw device file for the file system and builds a table of directories and files in memory. Then, this command writes the table to the backup media. In the second pass, the ufsdump command goes through the inodes in numerical order, reading the file contents and writing the data to the media.

Determining Device Characteristics

The ufsdump command needs to know only an appropriate block size and how to detect the end of media.

Detecting the End of Media

The ufsdump command writes a sequence of fixed-size records. When the ufsdump command receives notification that a record was only partially written, it assumes that it has reached the physical end of the media. This method works for most devices. If a device is not able to notify the ufsdump command that only a partial record has been written, a media error occurs as the ufsdump command tries to write another record.

Note –

DAT devices and 8-mm tape devices detect end-of-media. Cartridge tape devices and 1/2–inch tape devices do not detect end-of-media.

The ufsdump command automatically detects the end-of-media for most devices. Therefore, you do not usually need to use the -c, -d, -s, and -t options to perform multivolume backups.

The only time you need to use the end-of-media options is when the ufsdump command does not understand the way the device detects the end-of-media or you are going to restore the files on a SunOS 4. 1 system with an the restore command. To ensure compatibility with the restore command, the size option can still force the ufsdump command to go to the next tape or diskette before reaching the end of the current tape or diskette.

Copying Data With ufsdump

The ufsdump command copies data only from the raw disk slice. If the file system is still active, anything in memory buffers is probably not copied. The backup done by ufsdump does not copy free blocks, nor does it make an image of the disk slice. If symbolic links point to files on other slices, the link itself is copied.

Role of the /etc/dumpdates File

The ufsdump command, when used with the -u option, maintains and updates the /etc/dumpdates file. Each line in the /etc/dumpdates file shows the file system backed up, the level of the last backup, and the day, date, and time of the backup. For example:

/dev/rdsk/c0t0d0s7               0 Mon Dec 10 16:26:10 2001
/dev/rdsk/c0t0d0s7               9 Tue Dec 11 16:45:14 2001
/dev/rdsk/c0t0d0s7               9 Wed Dec 12 16:54:47 2001

When you do an incremental backup, the ufsdump command checks the /etc/dumpdates file to find the date of the most recent backup of the next lower level. Then, this command copies to the media all files that were modified since the date of that lower-level backup. After the backup is complete, a new information line, which describes the backup you just completed, replaces the information line for the previous backup at that level.

Use the /etc/dumpdates file to verify that backups are being done. This verification is particularly important if you are having equipment problems. If a backup cannot be completed because of equipment failure, the backup is not recorded in the /etc/dumpdates file.

If you need to restore an entire disk, check the /etc/dumpdates file for a list of the most recent dates and levels of backups so that you can determine which tapes you need in order to restore the entire file system.

Note –

The /etc/dumpdates file is a text file that can be edited, but edit it only at your own risk. If you make changes to the file that do not match your archive tapes, you might not be able to find the tapes (or files) you need.

Backup Device (dump-file) Argument

The dump-file argument (to the -f option) specifies the destination of the backup, which can be one of the following:

Use this argument when the destination is not the default local tape drive /dev/rmt/0. If you use the -f option, then you must specify a value for dump-file.

Note –

The dump-file argument can also point to a file on a local or remote disk, which, if used by mistake, can fill up a file system.

Local Tape or Diskette Drive

Typically, the dump-file argument specifies a raw device file for a tape device or diskette. When the ufsdump command writes to an output device, it creates a single backup file that might span multiple tapes or diskettes.

You specify a tape device or diskette on your system by using a device abbreviation. The first device is always 0. For example, if you have a SCSI tape controller and one QIC-24 tape drive that uses medium-density formatting, use this device name:


When you specify a tape device name, you can also type the letter “n” at the end of the name to indicate that the tape drive should not rewind after the backup is completed. For example:


Use the “no-rewind” option if you want to put more than one file onto the tape. If you run out of space during a backup, the tape does not rewind before the ufsdump command asks for a new tape. For a complete description of device naming conventions, see Backup Device Names.

Remote Tape or Diskette Drive

You specify a remote tape device or diskette by using the syntax host:device. The ufsdump command writes to the remote device when root on the local system has access to the remote system. If you usually run the ufsdump command as root, the name of the local system must be included in the /.rhosts file on the remote system. If you specify the device as user@host:device, the ufsdump command tries to access the device on the remote system as the specified user. In this case, the specified user must be included in the /.rhosts file on the remote system.

Use the naming convention for the device that matches the operating system for the system on which the device resides, not the system from which you run the ufsdump command. If the drive is on a system that is running a previous SunOS release (for example, 4.1.1), use the SunOS 4.1 device name (for example, /dev/rst0). If the system is running Solaris software, use the SunOS 5.9 convention (for example, /dev/rmt/0).

Using Standard Output With the ufsdump Command

When you specify a dash (-) as the dump-file argument, the ufsdump command writes to standard output.

Note –

The -v option (verify) does not work when the dump-file argument is standard output.

You can use the ufsdump and ufsrestore commands in a pipeline to copy a file system by writing to the standard output with the ufsdump command and reading from standard input with the ufsrestore command, as shown in this example:

# ufsdump 0f - /dev/rdsk/c0t0d0s7 | (cd /home; ufsrestore xf -)

Specifying Files to Back Up

You must always include filenames as the last argument on the command line. This argument specifies the source or contents of the backup.

For a file system, specify the raw device file as follows:


You can specify the file system by its mount point directory (for example, /export/home), as long as there is an entry for it in the /etc/vfstab file.

For a complete description of device naming conventions, see Backup Device Names.

For individual files or directories, type one or more names separated by spaces.

Note –

When you use the ufsdump command to back up one or more directories or files (rather than a complete file system), a level 0 backup is done. Incremental backups do not apply.

Specifying Tape Characteristics

If you do not specify any tape characteristics, the ufsdump command uses a set of defaults. You can specify tape cartridge (c), density (d), size (s), and number of tracks (t). Note that you can specify the options in any order as long as the arguments that follow match the order of the options.

Limitations of the ufsdump Command

The ufsdump command cannot do the following:

Options and Arguments for the ufsdump Command

This section describes in detail the options and arguments for the ufsdump command. The syntax for the ufsdump command is as follows:

/usr/sbin/ufsdump options arguments filenames 


Is a single string of one-letter option names. 


Identifies option arguments and might be multiple strings. The option letters and the arguments that go with them must be in the same order. 


Identifies the files to back up. These arguments must always come last. 

Default ufsdump Options

If you run the ufsdump command without any options, use this syntax:

# ufsdump filenames

The ufsdump command uses these options and arguments, by default:

ufsdump 9uf /dev/rmt/0 filenames

These options do a level 9 incremental backup to the default tape drive at its preferred density.

Options for the ufsdump Command

The following table describes the options for the ufsdump command.

Table 50–1 Options for the ufsdump Command




Dump level. Level 0 is for a full backup of the complete file system that is specified by filenames. Levels 1–9 are for incremental backups of files that have changed since the last lower-level backup.

a archive-file

Archive file. Stores (archives) a backup table of contents in a specified file on the disk. The file can be understood only by the ufsrestore command, which uses it to determine whether a file to be restored is present in a backup file, and if so, on which volume of the media it resides.

b factor

Blocking factor. Specifies the number of 512-byte blocks to write to tape at a time. 


Cartridge. Back up to cartridge tape. When end-of-media detection applies, this option sets the block size to 126. 

d bpi

Tape density. Use this option only when the ufsdump command cannot detect the end of the media.


Diskette. Backs up to diskette. 

f dump-file

Dump file. Writes the files to the destination that is specified by dump-file instead of the default device. If the file is specified as user@system:device, the ufsdump command attempts to execute as the specified user on the remote system. The specified user must have a /.rhosts file on the remote system that allows the user who is invoking the command on the local system to access the remote system.


Autoload. Use this option if you have an autoloading (stackloader) tape drive. When the end of a tape is reached, this option takes the drive offline and waits up to two minutes for the tape drive to be ready again. If the drive is ready within two minutes, it continues. If the drive is not ready after two minutes, it prompts the operator to load another tape. 


Notify. When intervention is needed, this option sends a message to all terminals of all users in the sys group.


Offline. When finished with a tape or diskette, this option takes the drive offline, rewinds (if tape), and if possible removes the media (for example, ejects a diskette or removes an 8-mm autoloaded tape). 

s size

Size. Specifies the length of tapes in feet or for diskettes, the number of 1024-byte blocks. Use this option only when the ufsdump command cannot detect the end of the media.


Estimates the size of the backup. Determines the amount of space that is needed to perform the backup, without actually doing it, and outputs a single number that indicates the estimated size of the backup in bytes. 

t tracks

Tracks. Specifies the number of tracks for a 1/4-inch cartridge tape. Use this option only when the ufsdump command cannot detect the end of the media.


Updates the dump record. A completed backup of a file system adds an entry to the /etc/dumpdates file. The entry indicates the device name for the file system's disk slice, the dump level (0–9), and the date. No record is written when you do not use the u option or when you back up individual files or directories. If a record already exists for a backup at the same level, it is replaced.


Verify. After each tape or diskette is written, verifies the contents of the media against the source file system. If any discrepancies occur, prompts the operator to mount new media, then repeats the process. Use this option only on an unmounted file system, because any activity in the file system causes the ufsdump command to report discrepancies.


Warning. Lists the file systems that appear in the /etc/dumpdates file that have not been backed up within a day. When you use this option, all other options are ignored.


Warning with highlight. Shows all the file systems that appear in the /etc/dumpdates file and highlights those file systems that have not been backed up within a day. When you use this option, all other options are ignored.

Note –

The /etc/vfstab file does not contain information about how often to back up a file system.

The ufsdump Command and Security Issues

If you are concerned about security, you should do the following:

Options and Arguments for the ufsrestore Command

The syntax of the ufsrestore command is:

ufsrestore options arguments filenames


Is a single string of one-letter option names. You must choose one and only one of these options: i, r, R, t, or x. The additional options listed in Table 50–3 are optional.


Follows the option string with the arguments that match the options. The option letters and the arguments that go with them must be in the same order. 


Specifies the files to be restored as arguments to the x or t options. These arguments must always come last.

You must use one (and only one) of the ufsrestore command options shown in the following table.

Table 50–2 One Required Option for the ufsrestore Command




Interactive. Runs the ufsrestore command in an interactive mode. In this mode, you can use a limited set of shell-like commands to browse the contents of the media and select individual files or directories to restore. For a list of interactive commands, see Table 50–4.


Recursive. Restores the entire contents of the media into the current working directory (which should be the top level of the file system). Information used to restore incremental dumps on top of the full dump (for example, restoresymtable) is also included. To completely restore a file system, use this option to restore the full (level 0) dump and each subsequent incremental dump. Although this option is intended for a new file system (that was just created with the newfs command), files not on the backup media are preserved.


Resume restoring. Prompts for the volume from which to resume restoring and restarts from a checkpoint. You rerun the ufsrestore command with this option after a full restore (r option) is interrupted.

x [filenames]


Extract. Selectively restores the files you specify by the filenames argument. filenames can be a list of files and directories. All files under a specified directory are restored unless you also use the h option. If you omit filenames or enter “.” for the root directory, all files on all volumes of the media (or from standard input) are restored. Existing files are overwritten, and warnings are displayed.

t [filenames]

Table of contents. Checks the files that are specified in the filenames argument against the media. For each file, lists the full file name and the inode number (if the file is found) or indicates that the file is not on the “volume” (meaning any volume in a multivolume dump). If you do not enter the filenames argument, all files on all volumes of the media are listed (without distinguishing on which volume files are located). If you also use the h option, only the directory files that are specified in filenames, not their contents, are checked and listed. The table of contents is read from the first volume of the media, or, if you use the a option, from the specified archive file. This option is mutually exclusive with the x and r options.

Additional ufsrestore options are described in the following table.

Table 50–3 Additional Options for the ufsrestore Command



a archive-file [filenames]

Takes the dump table of contents from the specified archive-file instead of from the media (first volume). You can use this option in combination with the t, i, or x options to see if files are on the media without having to mount any media. If you use it with the x and interactive extract options, you are prompted to mount the appropriate volume before extracting the file(s).

b factor

Blocking factor. Specifies number of 512-byte blocks read from tape at a time. By default, the ufsrestore command tries to figure out the block size that was used in writing the tape.


Debug. Turns on debugging messages. 

f backup-file

Backup file. Reads the files from the source indicated by backup-file, instead of from the default device file /dev/rmt/0m. If you use the f option, you must specify a value for backup-file. When backup-file is of the form system:device, the ufsrestore command reads from the remote device. You can also use the backup-file argument to specify a file on a local or remote disk. If backup-file is `-', the files are read from standard input.


Turns off directory expansion. Only the directory file you specify is extracted or listed. 


Restores specified files into the current directory on the disk regardless of where they are located in the backup hierarchy and renames them with their inode number. For example, if the current working directory is /files, a file in the backup named ./dready/fcs/test with inode number 42, is restored as /files/42. This option is useful only when you are extracting a few files.

s n

Skips to the nth backup file on the media (first volume). This option is useful when you put more than one backup on a single tape.


Verbose. Displays the names and inode numbers of each file as it is restored. 


Continues when errors occur while reading the media and tries to skip over bad blocks instead of stopping and asking whether to continue. This option tells the command to assume a yes response. 

The following table describes ufsrestore's interactive commands.

Table 50–4 Commands for Interactive Restore



ls [directory-name]

Lists the contents of either the current directory or the specified directory. Directories are marked by a / suffix. Entries in the current list to be restored (extracted) are marked by an * prefix. Inode numbers are shown if the verbose option is used.

cd directory-name

Changes to the specified directory in the backup hierarchy. 

add [filename]

Adds the current directory or the specified file or directory to the list of files to extract (restore). If you do not use the h option, all files in a specified directory and its subdirectories are added to the list. All the files you want to restore to a directory might not be on a single backup tape or diskette. You might need to restore from multiple backups at different levels to get the latest versions of all the files.

delete [filename]

Deletes the current directory or the specified file or directory from the list of files to extract (restore). If you do not use the h option, all files in the specified directory and its subdirectories are deleted from the list. The files and directories are deleted only from the extract list you are building. They are not deleted from the media or the file system.


Extracts the files in the list and restores them relative to the current working directory on the disk. Specify 1 when you are asked for a volume number for a single-volume backup. If you are doing a multitape or multidiskette restore and restoring a small number of files, start with the last tape or diskette instead.


Displays a list of commands you can use in interactive mode. 


Displays the path name of the current working directory in the backup hierarchy. 


Quits interactive mode without restoring any additional files. 


Lets you set the mode for files to be restored to match the mode of the root directory of the file system from which they were backed up. You are prompted with: set owner/mode for '.' [yn]? Type y (for yes) to set the mode (permissions, owner, times) of the current directory to match the root directory of the file system from which they were backed up. Use this mode when you restore a complete file system.

Type n (for no) to leave the mode of the current directory unchanged. Use this mode when you restore part of a backup to a directory other than the directory from which the files were backed up.


Turns on or off the verbose option (which can also be entered as v on the command line outside of interactive mode). When verbose is on, the interactive ls command lists inode numbers and the ufsrestore command displays information on each file as it is extracted.


Displays the backup header from the tape or diskette.