Added howto from Patrick Walsh

[dump.git] / examples / howto / ultra-mini-howto

Stelian,

    I just got dump running on my system backing up a handful of unix
servers and at the end of it I wrote a quick and dirty document that lays
out the answers to some of the questions that I had.  I don't want to
maintain it or get a flood of e-mail from people asking for help on it, so I
signed it, but intentionally didn't put an e-mail address.

    You are welcome to make this prettier, totally discard it, or put it up
on the web page.  I hope it is accurate and relieves some of the common
questions from the list.

..Patrick




Dump/Restore Ultra-Mini-FAQ

Disclaimer: I am not an expert in dump/restore.  In fact,
I'm a newbie.  But I've been picking things up as I
implement it here and I wanted to pass some of those
things along in the form of a very basic HOWTO.

-Patrick Walsh

1) Introduction/ Non-rewinding device
2) Dump command line
3) Sending 2 or more filesystems to a tape
4) Compressing dumps on the fly
5) The "nodump" file and directory attribute.
6) Restoring your dumps (including compressed).
7) How to confirm a backup
8) Example backup script

 1) Introduction/ Non-rewinding device

You use dump to backup to a file or a tape device.  If
you're backing up to a tape device, then the first thing
you need to understand is that there are two devices
that refer to your tape drive.  There is the "rewinding"
device and the "non-rewinding" device.

I wish I could tell you an easy way to figure out what
your device names are, but I don't know one.  On my
local box I had a /dev/tape device that linked to
/dev/st0.  It turns out that /dev/st0 is my "rewinding"
tape drive.  If I write to this device it will always
rewind before starting to write.  This means that if
you try to dump two filesystems, only the second one
will be stored.  If your tape device is /dev/st0, like
mine, then your non-rewinding tape device is probably
/dev/nst0.

Anyway, through the rest of this I will refer to $TAPE
and $RWTAPE.  $TAPE is the non-rewinding device (in my
case /dev/nst0) and $RWTAPE is the rewinding tape (in my
case /dev/st0 and /dev/tape).  $FS is the filesystem you
are backing up, such as /dev/hda1.

 2) What options should I use?

Use the man page to figure out what options to send
to dump.  I use "dump 0uanf $TAPE $FS".

  u=update /etc/dumpdates after a successful dump
  a=auto-size -- bypass all tape length calculations and
    write until eof
  n=notify 'operators' group when dump needs attention
  f=backup to file or device specified, or - for stdout

 3) You want to send two or more filesystems to the tape.

OK, rewind using the mt command, then dump multiple times
to the non-rewinding device, and you're done:

mt -f $TAPE rewind
dump 0uanf $TAPE $FS1
dump 0uanf $TAPE $FS2
etc.

Check the man page of mt if you want to know how to eject
the tape or retension it or anything.

 4) You want to compress your dumps on the fly.  No
problem.  Send your backup to STDOUT and manipulate it
from there.  It's easier if you're sending your output to
the hard drive:

dump 0uanf - $FS | gzip -c > /backup/outfile.dump.gz

You want that to be written to the tape on the fly?  Try
this:

mt -f $TAPE rewind
dump 0uanf - $FS |gzip -c |dd if=- of=$TAPE

[ You can also use the -z or -J options of dump in the 
  recent versions to enable internal compression - stelian ]

 5) You read the man page and you're wondering what the
heck a "nodump" flag is.  For example, how can you get
dump to stop backing up /tmp or ~/.netscape/cache.  You
have two options: either exclude the inode in your dump
command, or flag the files and directories with the
"nodump" flag.  To flag /tmp, for example, do this:

chattr -R +d /tmp

Want more details?  Try 'man chattr' and 'man lsattr'.

 6) You want to know how to restore your backup.

Read the restore man page.  But barring that, the easy way
is to use restore in interactive mode.  If you have three
filesystems on one tape and you want to restore files from
the second one, you need to do this:

mt -f $TAPE rewind
mt -f $TAPE fsf 1     # skip forward one file
restore -if $TAPE

OK, suppose now that you used the commands in section 4 to
compress the dump file before it was written to disk.  Use
this command:

mt -f $TAPE rewind
mt -f $TAPE fsf 1
dd if=$TAPE of=- |gzip -dc |restore -rf -

Obviously if you dumped to a file instead of a tape it is
much easier:

gzip -dc $filename |restore -rf -

 7) How to confirm your backup

 Check out the restore man page and read up on the -C option.

 8) That about sums up my knowledge on the matter, but
I feel better having written something for other people to
look at so it doesn't take them quite so long to learn the
things I did.  I've included my backup script below.
There are much better ones floating around, so go find
someone else's and use theirs if mine won't work for you
or you don't understand it.


#!/bin/csh
# System backup script for NARNIA

# This is a script that will backup the entire hard drive
# to the NT server (not my choice) \\fs1.
#
# On each Sunday night, a full backup will be made
# of the hard drive and each day of the week thereafter an incremental
# backup will be made that captures only those changes since the night
# before.
# Each full backup will be sent to the local tape as well as to the
# NT machine.
#
# The files will be stored in partition-specific files with integer
# endings that specify the day of the week they were saved.  Files
# with zero on the end will always be full backups.

# Dump options:
#   a=auto-size -- bypass all tape length calculations and write until eof
#   f=write the backup to file or device specified or - for stdout
#   n=notify operators group when dump needs attention
#   u=update /etc/dumpdates after a successful dump

# Set variables that control the script.
setenv MOUNTPOINT '/root/fs1backup'
setenv OUTDIR '/root/fs1backup/narnia'
setenv TAPE '/dev/nst0'  # non-rewinding tape

# Auto-set variable that determines level of backup.
setenv DAY `date +'%w'`

# Mount the backup partition to /root/fs1backup
/usr/bin/smbmount \\\\fs1\\backup $MOUNTPOINT -o
"username=uname,password=pword"

# Delete files created on this day last week
rm -f $OUTDIR/*$DAY.dump.gz

# Do the actual backing up, one filesystem at a time.

# /dev/hda1 = /boot
/sbin/dump $DAY'uanf' - /dev/hda1 | gzip -c >$OUTDIR/boot-$DAY.dump.gz

# /dev/hda2 = /
/sbin/dump $DAY'uanf' - /dev/hda2 | gzip -c >$OUTDIR/root-$DAY.dump.gz

# /dev/hda3 = /usr
/sbin/dump $DAY'uanf' - /dev/hda3 | gzip -c >$OUTDIR/usr-$DAY.dump.gz

# /dev/hdb2 = /u1
/sbin/dump $DAY'uanf' - /dev/hdb2 | gzip -c >$OUTDIR/u1-$DAY.dump.gz


# OK, presumably everything is now backed up to \\fs1. On level 0
# dumps, lets backup to the local drive too.
if ($DAY == 0) then
 mt -f $TAPE retension
 foreach i ($OUTDIR/*0.dump.gz)
  dd if=$i of=$TAPE
 end
 mt -f $TAPE rewind
endif


# Unmount the backup partition, not needed outside of script
umount /root/fs1backup

# Explicitly free up the temporary variables
unsetenv DAY
unsetenv MOUNTPOINT
unsetenv OUTDIR
unsetenv TAPE


# RESTORE DIRECTIONS:
# If from tape:
#    dd if=$TAPE of=- | gzip -dc | restore -rf -
# or dd if=$TAPE |gzip -dc |restore -rf -
#
# Note: must queue tape to proper position first.  This
# is done by first rewinding then advancing to the proper
# file.  The order that files are written to tape is
# *probably* 0=/boot 1=/ 2=/usr 3=/u1
#
# Use mt to skip between them:
#  mt -f $TAPE rewind
# restore -if $TAPE   #now restoring /boot, probably
# mt -f $TAPE fsf 1
# restore -if $TAPE   #now restoring /
# mt -f $TAPE fsf 1
# restore -if $TAPE   #now restoring /usr
# #etc.
#
# Otherwise:
#    gzip -dc $filename | restore -rf -