vbackup, vcat, vftp, vmount, vnfs – back up Unix file systems to
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
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:|
(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.
Set backup mount point:
−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.|
−n No-op mode: do not write any blocks to the server
this name is also used in the printed mount command. The default
is the name returned by sysname (see getuser(3)).|
−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 progress
at a time.
When vbackup finishes, it prints a single line of the form
Status interval: every secs seconds, print a line tracking progress
of the backup.
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 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:
mount /host/yyyy/mmdd/mtpt score yyyy/mmdd/hhmm|
−E Disable ‘encrypted’ handles. By default handles are encrypted
with a random key to avoid leaking information 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 loopback interface
−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 service, no other local users can access
−R Print all NFS and NFS mount RPCs to standard error.
−V Print all Venti transactions to standard error.
Serve requests on addr (see above).|
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.|
−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.)
Set the number of blocks stored by the in-memory venti cache.|
−r Respond to all requests with a Sun RPC rejection. This is useful
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
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 be created if necessary.
If /dev/null is given as the score, an empty file system is mounted
at mtpt, excluding mtpt’s contents from view. Time is the modification
time to return for the directory mtpt, either a decimal number
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.)|
Reading the special file /dump/+refreshconfig causes vnfs to reload
config. The read returns either the string ok or an error message.
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.
Running on the server bob, back up the file system stored on /dev/da0s1a,
which is mounted on /home:|
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 :
% vbackup /dev/da0s1a|
mount /bob/2005/0510/home ffs:0123456789abcdef... 2005/0510/0831
% cat config|
mount /bob/2005/0510 ffs:0123456789abcdef
Mount the backups on a client machine using vmount:
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
(Users of fancy shells may need to quote the address argument.)
# vmount udp!yourserver!nfs /dump|
# ls /dump/bob/2005