File systems Backup Management

Compress command.
Compress command compresses a file and returns the original file with .z extension, to uncompress this filename.Z file use uncompress filename command. syntax for compress command is
compress options files

Options
• -bn limit the number of bits in coding to n.
• -c write to standard output (do not change files).
• -f compress conditionally, do not prompt before overwriting files.
• -v Print the resulting percentage of reduction for files.

Uncompress command.
Uncompress file uncompresses a file and return it to its original form.
syntax is
uncompress filename.Z this uncompresses the compressed file to its original name.

Options
• -c write to standard output without changing files

Cpio command.
cpio command is useful to backup the file systems. It copy file archives in from or out to tape or disk, or to another location on the local machine. Its syntax is
cpio flags [options]

It has three flags, -i, -o, -p
• cpio -i [options] [patterns]
  • cpio -i copy in files who names match selected patterns.
  • If no pattern is used all files are copied in.
  • It is used to read from a tape or disk.

• cpio -o [options] [patterns]
  • Copy out a list of files whose name are given on standard output.
  • It is used to write to a tape or disk.

• cpio -p [options] [patterns]
  • copy files to another directory on the same system.

Options
• -a reset access times of input files.
• -A append files to an archive (must use with -o).
• -b swap bytes and half-words. Words are 4 bytes.
• -B block input or output using 5120 bytes per record.
• -c Read or write header information as Ascii character.
• -d create directories as needed.
• -l link files instead of copying.
• -o file direct output to a file.
• -r rename files interactively.
• -R ID reassign file ownership and group information to the user's login ID.
• -V print a dot for each file read or written.
• -s swap bytes.
• -S swap half bytes.
• -v print a list of filenames.

Examples
• find . -name "*.old" -print | cpio -ocvB > /dev/rst8 will backup all *.old files to a tape in /dev/rst8
• cpio -icdv "save"" < /dev/rst8 will restore all files whose name contain "save"
• find . -depth -print | cpio -padm /mydir will move a directory tree.

Dump command is useful to backup the file systems.
dump command copies all the files in filesystem that have been changed after a certain date. It is good for incremental backups. This information about date is derived from /var/adm/dumpdates and /etc/fstab .
syntax for HP-UX dump is
/usr/sbin/dump [option [argument ...] filesystem]

Restore command.
Restore and ufsrestore command restores files backed up with dump command.
Syntax is
restore options arguments files-dirs

Options
• -r will read and restore the entire tape.
• -x will extract all files and directory listed and restore in current directory.
• -t will type the names of the listed files as they appear on terminal.
• -f must be followed by a device name, otherwise default device is assumed.
• -i will launch interactive mode to restore the files you want to pick.

Pack command.
pack command compacts each file and combine them together into a filename.z file. The original file is replaced. Pcat and unpack will restore packed files to their original form.
Syntax is
Pack options files

Options
• - Print number of times each byte is used, relative frequency and byte code.
• -f Force the pack even when disk space isn't saved.

• To display Packed files in a file use pcat command
  pcat filename.z
• To unpack a packed file use unpack command as unpack filename.z .

Tar command.
tar command creates an archive of files into a single file.
Tar copies and restore files to a tape or any storage media. Synopsis of tar is
tar [options] [file]

Examples:
tar cvf /dev/rmt/0 /bin /usr/bin creates an archive of /bin and /usr/bin, and store on the tape in /dev/rmt0.
tar tvf /dev/rmt0 will list the tape's content in a /dev/rmt0 drive.
tar cvf - 'find . -print' > backup.tar will creates an archive of current directory and store it in file backup.tar.

Functions:
• c creates a new tape.
• r append files to a tape.
• t print the names of files if they are stored on the tape.
• x extract files from tape.

Options:
• b n use blocking factor of n.
• l print error messages about links not found.
• L follow symbolic links.
• v print function letter (x for extraction or a for archive) and name of files.

Mt command is used for tape and other device functions like rewinding, ejecting, etc. It give commands to tape device rather than tape itself. Mt command is BSD command and is seldom found in system V unix versions.
syntax is
mt [-t tapename] command [count]

mt for HP-UX accept following commands
• eof write count EOF marks.
• fsf Forward space count files.
• fsr Forward space count records.
• bsf Backward space count files.
• bsr Backward space count records.
• rew Rewind tape.
• offl Rewind tape and go offline.
• eod Seek to end of data (DDS and QIC drives only).
• smk Write count setmarks (DDS drives only).
• fss Forward space count setmarks (DDS drives only).
• bss Backward space count setmarks (DDS drives only).
• Examples
  • mt -t /dev/rmt/0mnb rew will rewind the tape in this device.
  • mt -t /dev/rmt/0mnb offl will eject the tape in this device.

These following are some other issues concerning backups.

1. An effective backup strategy is an ongoing process.
2. The simpliest backup scheme is to copy all the files on a media, called full backup.
3. Copy only those files which were changed since last backup, called incremental backup.
4. Always label on media before what you are going to backup in that media.
5. Know where the media is and keep a handy procedure on "how to backup and restore."
6. Write protect media.
7. Take security of media into account. A stolen/lost tape of full backup is full access to system.

Magnetic Tape

Magnetic tapes are the most used media for backup. 8mm and 4mm tapes are most common backup medium for Unix systems. 8mm tapes were originally designed for video uses (8mm video camcorder), media holds upto 2GB of data. If your system needs more then 1 tape for backup then a stacker which can hold upto ten tapes along with software is very common. 4mm tapes which are smaller can hold more data since it is newer technology, upto 4GB. Another type of very famous upcoming media is DLT tapes, DLT tapes normally comes with all the hardware and software. All you have to do is make sure that there are enough tapes and schedule the backup.


Floppy disks

Floppy disks are found on most computer systems. Very inexpensive and reliable but their capacity is very small. Floppy disks are only good for emergency booting of system. Backup on floppies can run into several hundred or thousands of floppies each time.


Hard Disks