VBACKUP(8) VBACKUP(8)
NAME
vbackup, vcat, vftp, vmount, vnfs - back up Unix file
systems to Venti
SYNOPSIS
vbackup [ -DVinv ] [ -M mtpt ] [ -m host ] [ -s secs ] [ -w
n ] disk [ score ]
vcat [ -z ] disk | score > disk
vftp score | disk
vmount [ -v ] addr mtpt
vnfs [ -ELLRVir ] [ -a addr ] [ -b blocksize ] [ -c
cachesize ] config
DESCRIPTION
These programs back up and restore standard Unix file system
images stored in venti(8). Images stored in venti are named
by scores, which consist of a file system type followed by a
colon and forty hexadecimal digits, as in:
ffs:0123456789abcdef0123456789abcdef01234567
(The hexadecimal data is the SHA1 hash of the Venti root
block representing the file system image.)
These programs expect the environment variable $venti to be
set to the network address of the Venti server to use (for
example, yourhost or tcp!yourhost!venti).
Vbackup copies the file system stored on disk to the Venti
server and prints the score for the newly-stored image. The
argument disk should be a disk or disk partition device that
would be appropriate to pass to mount(8).
The optional argument score is the score of a previous
backup of the disk image. If score is given, vbackup will
not write to Venti any blocks that have not changed since
the previous backup. This is only a speed optimization:
since the blocks are already stored on Venti they need not
be sent to the Venti server again.
The options to vbackup are:
-D Turn on debugging output.
-V Trace interactions with Venti server.
Page 1 Plan 9 (printed 4/26/24)
VBACKUP(8) VBACKUP(8)
-m host
-M mtpt Set names used to construct the path in the
mount command. The default host is the name returned by
sysname (see getuser(3)). The default mtpt is the place
where disk is currently mounted.
Set backup mount point:
this name is also used in the printed mount command.
The default is the name returned by sysname (see
getuser(3)).
-n No-op mode: do not write any blocks to the server
-i Read scores incrementally from the previous backup as
needed, rather than prefetching them.
-v Print verbose output.
-w n Write parallelism: keep n writes to the server in pro-
gress at a time.
-s secs
Status interval: every secs seconds, print a line
tracking progress of the backup.
When vbackup finishes, it prints a single line of the form
mount /host/yyyy/mmdd/mtpt score yyyy/mmdd/hhmm
This line is a valid configuration line for vnfs (q.v.).
Mntpath is the path on which disk is currently mounted.
Vcat writes the named disk image to standard output. Unused
file system blocks are printed zeroed regardless of their
actual content.
By default, vcat will assume that its standard output is
seekable (i.e., it has been redirected to a file or disk)
and seek over unused blocks instead of writing to them. The
-z option causes vcat to zero unused blocks instead.
Vftp presents an ftp(1)-like interface to a physical or
backed-up disk image. It is used mainly for debugging.
Type help at the vftp> prompt for a list of commands.
Vmount mounts the NFS service at the network connection
address onto mountpoint. On most operating systems, vmount
must be run by the user root. Because address is passed to
the host OS kernel rather than interpreted by dial(3), it
must be only an IP address, not a full dial address.
Vnfs serves, using the NFS version 3 protocol, one or more
Page 2 Plan 9 (printed 4/26/24)
VBACKUP(8) VBACKUP(8)
disk images in a synthetic tree defined by the configuration
file config. Vnfs serves both NFS mount protocol and NFS
protocol RPCs at addr (default udp!*!nfs). The options are:
-E Disable `encrypted' handles. By default handles are
encrypted with a random key to avoid leaking informa-
tion about the backed-up file systems. If encryption
is disabled, the NFS handles exposed to the client may
leak information about the root scores of the disks as
well as inode numbers.
-L Local service only: serve only requests from the loop-
back interface (127.0.0.1).
-LL Local service only, with paranoia: serve only requests
from loopback, and only from the first source port that
sends a request. This option is intended to be used to
make sure that once the local host has mounted the ser-
vice, no other local users can access it.
-R Print all NFS and NFS mount RPCs to standard error.
-V Print all Venti transactions to standard error.
-a addr
Serve requests on addr (see above).
-b blocksize
Set block size used by the in-memory venti block cache.
Must be as large as the maximum block size in any file
system mentioned in the configuration.
-c cachesize
Set the number of blocks stored by the in-memory venti
cache.
-i Run in ``insecure'' mode, allowing remote root users to
use uid and gid 0 and read any file. (Normally, remote
root is mapped to uid and gid -1 and has no special
permissions.)
-r Respond to all requests with a Sun RPC rejection. This
is useful during debugging.
Config is a text file describing the backup hierarchy for
vnfs to serve. Lines beginning with a sharp (#) are
ignored. The rest of the file is a sequence of commands,
one per line. The commands are:
mount mtpt score time
Add the file system with the given score to the tree at
the mount point mtpt. The path to the mount point will
Page 3 Plan 9 (printed 4/26/24)
VBACKUP(8) VBACKUP(8)
be created if necessary. If /dev/null is given as the
score, an empty file system is mounted at mtpt, exclud-
ing mtpt's contents from view. Time is the modifica-
tion time to return for the directory mtpt, either a
decimal number of seconds since the epoch or a string
of the form yyyy/mmdd/hhmm giving the year, month, day,
hour, and minute. (Vnfs does not use the modification
time of the root in order to avoid accessing every
mounted file system on common actions like ls -l
/dump/sys/2005.)
allow ip[/mask]
deny ip[/mask]
These two commands define access permissions based on
IP address. The optional mask can be a decimal number
(24) or an equivalent IP mask (255.255.255.0). Each
request is filtered through the rules listed in the
configuration file. The first rule that matches is
used. If any allow or deny rules are given, the
default action is to reject the request. In the
absence of any rules, the default action is to accept
all requests.
Reading the special file /dump/+refreshconfig causes vnfs to
reload config. The read returns either the string ok or an
error message.
EXAMPLES
Running on the server bob, back up the file system stored on
/dev/da0s1a, which is mounted on /home:
% vbackup /dev/da0s1a
mount /bob/2005/0510/home ffs:0123456789abcdef... 2005/0510/0831
%
Serve that backup and a few others in a tree reminiscent of
Plan 9's dump file system, but hide each day's contents of
/tmp :
% cat config
mount /bob/2005/0510 ffs:0123456789abcdef... 2005/0510/0829
mount /bob/2005/0510/home ffs:0123456789abcdef... 2005/0510/0831
mount /bob/2005/0510/tmp /dev/null 1
mount /bob/2005/0511 ffs:0123456789abcdef... 2005/0511/0827
mount /bob/2005/0511/home ffs:0123456789abcdef... 2005/0511/0828
mount /bob/2005/0511/tmp /dev/null 1
% vnfs -b 16k -c 1k config
%
Mount the backups on a client machine using vmount:
Page 4 Plan 9 (printed 4/26/24)
VBACKUP(8) VBACKUP(8)
# vmount udp!yourserver!nfs /dump
# ls /dump/bob/2005
0510
0511
#
(Users of fancy shells may need to quote the address argu-
ment.)
Page 5 Plan 9 (printed 4/26/24)