fadedbee's questions

Debian keeps the keys required for a successful multistrap installation in a package called debian-archive-keyring.

(Multistrap is like debootstrap, but it can install packages from multiple repositories - e.g. the official repo plus your own organisation's repo. https://wiki.debian.org/Multistrap.)

Devuan also has the package debian-archive-keyring - it contains the Debian keys and does not contain the Devuan keys. In particular it doesn't contain the key 94532124541922FB.

There is no devuan-archive-keyring.

An example simple-config on https://wiki.debian.org/Multistrap includes a configuration line:

keyring=debian-archive-keyring

The specified keyring package is installed in the filesystem being built. Only packages from repositories signed with keys installed from keyring can be installed.

Which Devuan package contains the Devuan key 94532124541922FB?

If none, how do I use multistrap on Devuan?

I notice that multistrap is invoking apt-get with the parameters:

Getting package lists: APT_CONFIG=/tmp/multistrap.tRoXhw apt-get  
  -o Apt::Architecture=armhf 
  -o Dir::Etc::TrustedParts=/multistrap-devuan-ascii/etc/apt/trusted.gpg.d 
  -o Dir::Etc::Trusted=/multistrap-devuan-ascii/etc/apt/trusted.gpg 
  -o Apt::Get::Download-Only=true 
  -o Apt::Install-Recommends=false 
  -o Dir=/multistrap-devuan-ascii/ 
  -o Dir::Etc=/multistrap-devuan-ascii/etc/apt/ 
  -o Dir::Etc::Parts=/multistrap-devuan-ascii/etc/apt/apt.conf.d/ 
  -o Dir::Etc::PreferencesParts=/multistrap-devuan-ascii/etc/apt/preferences.d/ 
  -o APT::Default-Release='*' 
  -o Dir::State=/multistrap-devuan-ascii/var/lib/apt/ 
  -o Dir::State::Status=/multistrap-devuan-ascii/var/lib/dpkg/status 
  -o Dir::Cache=/multistrap-devuan-ascii/var/cache/apt/ update

Is there a way of overriding these variables without hacking the multistrap code?

If I could set Dir::Etc::TrustedParts or Dir::Etc::Trusted I could fix the issue.

I think I need to have the key 94532124541922FB in my keyring as multistrap is reporting:

W: GPG error: http://packages.roundr.devuan.org/merged ascii InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 94532124541922FB
W: The repository 'http://auto.mirror.devuan.org/merged ascii InRelease' is not signed.

I tried importing the key using:

user@host:~/multistrap$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 94532124541922FB
Executing: /tmp/apt-key-gpghome.wsOOsj4iqi/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-keys 94532124541922FB
key 94532124541922FB:
1 signature not checked due to a missing key
gpg: key 94532124541922FB: "Devuan Repository (Primary Devuan signing key) <[email protected]>" 1 new signature
gpg: Total number processed: 1
gpg:         new signatures: 1

I wasn't sure if this was successful, so I tried:

user@host:~/multistrap$ gpg --list-keys
/home/user/.gnupg/pubring.kbx
--------------------------------
pub   rsa3072 2019-03-25 [SC] [expires: 2021-03-24]
      579B175CD95705FB9A6C3D271587404115319AFF
uid           [ultimate] User <[email protected]>
sub   rsa3072 2019-03-25 [E] [expires: 2021-03-24]

Which makes me think it has failed.

How do I get the key 94532124541922FB?

Update: I have discovered that apt-key has a different keyring from GPG and that GPG has different keyrings dependent on whther you're using sudo.

The key is there, with apt-key:

user@host:~/multistrap$ sudo apt-key adv --list-keys
Executing: /tmp/apt-key-gpghome.12skPKfRJz/gpg.1.sh --list-keys
/tmp/apt-key-gpghome.12skPKfRJz/pubring.gpg
-------------------------------------------
...
pub   rsa2048 2014-12-02 [SC]
      72E3CB773315DFA2E464743D94532124541922FB
uid           [ unknown] Devuan Repository (Primary Devuan signing key) <[email protected]>
sub   rsa2048 2014-12-02 [E]
sub   rsa4096 2016-04-26 [S]

pub   rsa4096 2016-10-06 [SC]
      CF1921B2D91C6435848E810099C46A90B1FB3B59
uid           [ unknown] Devuan ISO Toaster (Devuan GNU+Linux) <[email protected]>
sub   rsa4096 2016-10-06 [E]

pub   rsa4096 2017-09-04 [SC] [expires: 2022-09-03]
      E032601B7CA10BC3EA53FA81BB23C00C61FC752C
uid           [ unknown] Devuan Repository (Amprolla3 on Nemesis) <[email protected]>
sub   rsa4096 2017-09-04 [E] [expires: 2022-09-03]

but still multistrap complains:

user@host:~/multistrap$ sudo multistrap -a armhf -d /multistrap-devuan-ascii -f simple-config
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
    LANGUAGE = (unset),
    LC_ALL = (unset),
    LANG = "en_GB.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
multistrap 2.2.9 using simple-config
multistrap 2.2.9 using simple-config
Defaulting architecture to native: armhf
multistrap building armhf multistrap on 'armhf'
I: Downloading debian-archive-keyring 
Get:1 http://packages.roundr.devuan.org/merged ascii/main armhf debian-archive-keyring all 2017.5 [56.4 kB]
Fetched 56.4 kB in 0s (67.5 kB/s)           
Getting package lists: APT_CONFIG=/tmp/multistrap.QTx1QB apt-get  -o Apt::Architecture=armhf -o Dir::Etc::TrustedParts=/multistrap-devuan-ascii/etc/apt/trusted.gpg.d -o Dir::Etc::Trusted=/multistrap-devuan-ascii/etc/apt/trusted.gpg -o Apt::Get::Download-Only=true -o Apt::Install-Recommends=false -o Dir=/multistrap-devuan-ascii/ -o Dir::Etc=/multistrap-devuan-ascii/etc/apt/ -o Dir::Etc::Parts=/multistrap-devuan-ascii/etc/apt/apt.conf.d/ -o Dir::Etc::PreferencesParts=/multistrap-devuan-ascii/etc/apt/preferences.d/ -o APT::Default-Release='*' -o Dir::State=/multistrap-devuan-ascii/var/lib/apt/ -o Dir::State::Status=/multistrap-devuan-ascii/var/lib/dpkg/status -o Dir::Cache=/multistrap-devuan-ascii/var/cache/apt/ update
Get:1 http://packages.roundr.devuan.org/merged ascii InRelease [21.9 kB]
Ign:1 http://packages.roundr.devuan.org/merged ascii InRelease
Fetched 21.9 kB in 0s (34.5 kB/s)
Reading package lists... Done
W: GPG error: http://packages.roundr.devuan.org/merged ascii InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 94532124541922FB
W: The repository 'http://auto.mirror.devuan.org/merged ascii InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.

I have a flash drive, which is ten-percent full, but has been used extensively. (i.e. a large minority of blocks will contain random noise.)

In order to make a small, compressed image of this drive (if it were an HDD) I would dd if=/dev/zero of=/tmp/zeros.tmp bs=16M; rm /tmp/zeros.tmp. This fills all unused blocks with zeros, so that an image of the drive compresses well.

With a flash drive, would there be any advantage in writing 0xFFs to unused blocks, instead of zeros? i.e. is the flash drive clever enough to not rewrite a page that already contains 0xFFs?

I've installed PHP 5.6 from the PPA http://ppa.launchpad.net/ondrej/php/ubuntu.

All the packages are called php5.6-whatever.

There is no php5.6-pear in that PPA.

How can I install php5.6-pear?

How can I instruct Postgres to complete all "in-progress" transactions, but to delay starting new ones (without kicking clients off) until I have taken a ZFS or LVM snapshot (which takes less than a second).

e.g.

1. pause Postgres, waiting for "in-progress" transactions to complete
2. sync to disk
3. take ZFS/LVM snapshot
4. resume Postgres

I have a broken server, and backups of /etc/postgresql and /var/lib/postgresql.

The database I am looking for was used by a 2009 release of Redmine, if that makes any difference. https://www.redmine.org/

The backup of /etc/postgresql/postgresql.conf says:

data_directory = '/var/lib/postgresql/8.3/main'         # use data in another directory

Listing the backup of /var/lib/postgresql/8.3/main I see:

drwx------ 6 mysql scanner 4096 Nov 24  2009 base
drwx------ 2 mysql scanner 4096 Aug 15 07:40 global
drwx------ 2 mysql scanner 4096 Nov 23  2009 pg_clog
drwx------ 4 mysql scanner 4096 Nov 23  2009 pg_multixact
drwx------ 2 mysql scanner 4096 Nov 23  2009 pg_subtrans
drwx------ 2 mysql scanner 4096 Nov 23  2009 pg_tblspc
drwx------ 2 mysql scanner 4096 Nov 23  2009 pg_twophase
-rw------- 1 mysql scanner    4 Nov 23  2009 PG_VERSION
drwx------ 3 mysql scanner 4096 May 24 10:46 pg_xlog
-rw------- 1 mysql scanner  133 Jun 25  2014 postmaster.opts
-rw------- 1 mysql scanner   54 Jun 25  2014 postmaster.pid

(Ignore the ownership/group, they were messed up by the backup procedure.)

My concern is that only one file has an up-to-date modification time:

$ find . -mtime -10
./global
./global/pgstat.stat

Does this mean that the database data was written somewhere else, rather than into /var/lib/postgresql?

There does seem to be some significant disk usage:

$ du .
12  ./pg_clog
4   ./pg_twophase
12  ./pg_multixact/members
12  ./pg_multixact/offsets
28  ./pg_multixact
4   ./pg_tblspc
76  ./pg_subtrans
4   ./pg_xlog/archive_status
98312   ./pg_xlog
300 ./global
25428   ./base/16427
4280    ./base/11510
4500    ./base/11511
4280    ./base/1
38492   ./base
137244  .

Does this imply a non-empty database?

I'm just starting with Postgres.

This is a fresh install of Postgres 9.5 on Ubuntu 14.04 LTS. I used the apt repo from: http://www.postgresql.org/download/linux/ubuntu/

The intro page http://www.postgresql.org/docs/9.5/static/tutorial-createdb.html says that "-U" should work. It doesn't:

chris@blue:~$ psql -U postgres
psql: FATAL:  Peer authentication failed for user "postgres"

Yet, if I "su" to postgres, all is well:

chris@blue:~$ sudo su - postgres
postgres@blue:~$ psql
psql (9.5.2)
Type "help" for help.

postgres=# 

What have I misunderstood?

I have some problem network clients which send data too fast.

I want to slow them down, using iptables, or possibly tc.

I've seen iptables solutions like:

sudo iptables -A INPUT -m state --state RELATED,ESTABLISHED -m limit --limit 50/second --limit-burst 50 -j ACCEPT

but I think that the limit applies to everything which matches the rule, rather than per client address.

Is there a way of making this rule limit packets per client address?

I have a new PCI serial card, being used on a Ubuntu 14.04 box.

It's serial ports show up as /dev/ttyS4 and /dev/ttyS5.

$ dmesg | grep ttyS
[    0.732690] 00:03: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    0.733604] 0000:06:04.0: ttyS4 at I/O 0xd010 (irq = 16, base_baud = 115200) is a XScale
[    0.733700] 0000:06:04.0: ttyS5 at I/O 0xd000 (irq = 16, base_baud = 115200) is a XScale
$

I can set the baud rate of ttyS4 once after a reboot...

$ sudo /bin/stty -F /dev/ttyS4 115200
$

A second attempt yields an error...

$ sudo /bin/stty -F /dev/ttyS4 115200
/bin/stty: /dev/ttyS4: Input/output error
$

ttyS5 works fine...

$ sudo /bin/stty -F /dev/ttyS5 115200
$

and a second time...

$ sudo /bin/stty -F /dev/ttyS5 115200
$

When I need to choose a new port to use (internal to an organisation) I used to look in /etc/services. This is no longer sufficient, as Wireshark knows about many other ports that are not in /etc/services and therefore mislabels traffic.

I would like to get a list of all the (TCP and UDP) ports that Wireshark knows about, so that I can use a different one.

Where can I find (or how can I generate) this list?

Update, wrote a script:

#!/usr/bin/env python

import urllib2
response = urllib2.urlopen('http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt')
text = response.read()

for line in text.splitlines():
  words = line.split()
  if len(words) < 2: continue
  if words[1] != 'Unassigned': continue
  print words[0]

I have the following /etc/network/interfaces

# The loopback network interface
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
    bond-master bond0
    bond-primary eth0

auto eth1
iface eth1 inet manual
    bond-master bond0

auto bond0
iface bond0 inet static
    address 172.17.1.210
    netmask 255.255.255.0
    gateway 172.17.1.1
    bond-mode 1
    bond-miimon 100
    bond-slaves none

iface bond0:1 inet static
    address 172.17.1.215
    netmask 255.255.255.0
    gateway 172.17.1.1

If I try to manually bring up the alias interface bind0:1 I get the following error, but the interface does come up.

chris@abc1:~$ ifconfig bond0:1
bond0:1   Link encap:Ethernet  HWaddr d4:ae:52:ce:25:4b  
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

chris@abc1:~$ sudo ifup bond0:1
RTNETLINK answers: File exists
Failed to bring up bond0:1.
chris@abc1:~$ ifconfig bond0:1
bond0:1   Link encap:Ethernet  HWaddr d4:ae:52:ce:25:4b  
          inet addr:172.17.1.215  Bcast:172.17.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

If I try to bring the interface down, I get an error and the interface does not go down.

chris@abc1:~$ sudo ifdown bond0:1
ifdown: interface bond0:1 not configured
chris@abc1:~$ ifconfig bond0:1
bond0:1   Link encap:Ethernet  HWaddr d4:ae:52:ce:25:4b  
          inet addr:172.17.1.215  Bcast:172.17.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

I've replicated this behaviour on two fresh installs of Ubuntu 12.04.3, on two entirely separate networks (on different sites) with different topologies (i.e. eths connected to two switches at one site, and both eths connected to the same switch at another).

I have a similar alias interface working on another machine on eth0:1 - so I think I'm running the correct commands.

I also have a similar system working on Ubuntu 10.04 - but that was before 12.04 changed how bonding had to be configured.

Can anyone explain what I'm doing wrong? Is this a bug?

I have an existing Ubuntu 12.04 server, with all the packages that I need in /var/cache/apt/archives.

I have a fresh install of 12.04 at a customer site with (deliberately) no internet access.

How can I install all the packages I need (from the first machine's apt archive), without messing up apt on the second machine. (It may gain internet access later.) I have a USB drive.

Will installing with dpkg do the job? Would that mess up apt for future package installs? How would I get the order of installing 100+ packages correct?

What is the best way of getting a list of all files which have been written to, since power on?

Is a simple find (with mtime) best for this, or are there other ways?

(find won't list files which are written to, then deleted.)

I'm using Ubuntu Linux 12.04, if that makes a difference.

How does Linux software raid-1 work across disks of dissimilar performance.

Would a raid-1 across ssd and hdd partitions give me a mirror of the ssd contents while not impacting the read speed? I only need good read speed.

Or will it just distribute "reads" round-robin between the drives, giving poor read performance?

(I understand and accept that write performance will be as slow as a hdd.)

I want Upstart to do two things:

1. stop trying to respawn a failed process so fast
2. never give up trying to respawn

In an ideal world, upstart would try to restart a dead process after 1s, then double that delay on each attempt, until it reached an hour.

Is something like this possible?

On two different servers (with Ubuntu 12.04LTS AMD64) I have seen the following behaviour:

op - 10:50:05 up 305 days, 21:17,  1 user,  load average: 1.94, 2.52, 2.97
Tasks: 141 total,   2 running, 139 sleeping,   0 stopped,   0 zombie
Cpu(s): 41.5%us,  6.5%sy,  0.0%ni, 51.8%id,  0.0%wa,  0.2%hi,  0.1%si,  0.0%st
Mem:   8178432k total,  5753740k used,  2424692k free,   159480k buffers
Swap: 15625208k total,        0k used, 15625208k free,  4905292k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                               
    1 root      20   0 23928 2072 1216 S    0  0.0   0:56.42 init                                                                                  
    2 root      20   0     0    0    0 S    0  0.0   0:00.01 kthreadd                                                                              
    3 root      RT   0     0    0    0 S    0  0.0   0:01.23 migration/0                                                                           
    4 root      20   0     0    0    0 S    0  0.0   2:39.82 ksoftirqd/0                                                                           
    5 root      RT   0     0    0    0 S    0  0.0   0:00.00 watchdog/0                                                                            
    6 root      RT   0     0    0    0 S    0  0.0   0:02.99 migration/1                                                                           
    7 root      20   0     0    0    0 S    0  0.0   2:32.15 ksoftirqd/1                                                                           
    8 root      RT   0     0    0    0 S    0  0.0   0:00.00 watchdog/1                                                                            
    9 root      RT   0     0    0    0 S    0  0.0   0:11.67 migration/2                                                                           
   10 root      20   0     0    0    0 S    0  0.0  29:00.34 ksoftirqd/2  

The server is working fine, but top shows all processes as using 0% CPU. A reboot fixed this on an earlier machine, but I haven't yet tried it on this one.

I have tried top several times, and so am sure that I haven't accidentally pressed '<' or '>' to sort by a different column. Sorting the process list by all of the available columns, stills shows 0% CPU for all displayed processes.

What is going on? If this a kernel bug?

Update: If I use top -p <PID> for a known, busy process, top still displays 0% CPU for that process.

Update2: My point is that ALL processes are reporting 0% CPU usage ALL of the time.

I've done a fresh install of Ubuntu 12.04LTS, and installed the snmpd and snmp packages.

If I type:

snmpwalk -m ALL -v2c -c public localhost 1.3

I get swathes of errors, of the form:

Cannot adopt OID in SQUID-MIB: cacheClients ::= { cacheProtoAggregateStats 15 }
Cannot adopt OID in NET-SNMP-EXTEND-MIB: nsExtendLineIndex ::= { nsExtendOutput2Entry 1 }
Cannot adopt OID in NET-SNMP-EXTEND-MIB: nsExtendOutLine ::= { nsExtendOutput2Entry 2 }
Cannot adopt OID in UCD-SNMP-MIB: laIndex ::= { laEntry 1 }
Cannot adopt OID in UCD-SNMP-MIB: laNames ::= { laEntry 2 }
Cannot adopt OID in UCD-SNMP-MIB: laLoad ::= { laEntry 3 }
Cannot adopt OID in UCD-SNMP-MIB: laConfig ::= { laEntry 4 }
Cannot adopt OID in UCD-SNMP-MIB: laLoadInt ::= { laEntry 5 }
Cannot adopt OID in UCD-SNMP-MIB: laLoadFloat ::= { laEntry 6 }
Cannot adopt OID in UCD-SNMP-MIB: laErrorFlag ::= { laEntry 100 }
Cannot adopt OID in UCD-SNMP-MIB: laErrMessage ::= { laEntry 101 }
Cannot adopt OID in NET-SNMP-AGENT-MIB: nsNotifyRestart ::= { netSnmpNotifications 3 }
Cannot adopt OID in NET-SNMP-AGENT-MIB: nsNotifyShutdown ::= { netSnmpNotifications 2 }
Cannot adopt OID in NET-SNMP-AGENT-MIB: nsNotifyStart ::= { netSnmpNotifications 1 }

There a literally hundreds of these.

If snmp doesn't even like the distro-included MIBs, what chance to I have of getting my own used? (I get the same form of error with my own MIB, on a different machine, which is why I set up a clean install to test the distro's sanity.)

Do other distros have this issue? Is there something obvious that I am overlooking here?

How do you redirect (one way only) udp packets to another host using netcat?

nc -l -u 0.0.0.0 12345 | nc -u 192.168.1.128 12345

stops after successfully redirecting the first packet.

(Note: an iptables solution would also be useful.)

Thanks,

Chris.

I want to use ssh port forwarding. I haven't used this feature for a few years, so I may have forgotten something obvious, or OS defaults may have changed.

I have tried this on three different machines (all Ubuntu 9.10). The debug says that it is opening the ports for listening. They must be going away immediately and silently.

I've checked that I can reach 192.168.1.8:80 from my local machine.

There's probably a very simple reason, but I've not found it in 20 minutes of googling.

Any idea what the problem could be?

Thanks,

Chris.

root@chris-desktop:~# ssh -v -L 3142:192.168.1.8:80 yellow.example.com
OpenSSH_5.1p1 Debian-6ubuntu2, OpenSSL 0.9.8g 19 Oct 2007
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to yellow.example.com [199.82.114.103] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/identity type -1
debug1: identity file /root/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /root/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.1p1 Debian-6ubuntu2
debug1: match: OpenSSH_5.1p1 Debian-6ubuntu2 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.1p1 Debian-6ubuntu2
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-cbc hmac-md5 none
debug1: kex: client->server aes128-cbc hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'yellow.example.com' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:9
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Trying private key: /root/.ssh/identity
debug1: Offering public key: /root/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 277
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
debug1: Local connections to LOCALHOST:3142 forwarded to remote address 192.168.1.8:80
debug1: Local forwarding listening on ::1 port 3142.
debug1: channel 0: new [port listener]
debug1: Local forwarding listening on 127.0.0.1 port 3142.
debug1: channel 1: new [port listener]
debug1: channel 2: new [client-session]
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env LANG = en_GB.UTF-8
Linux yellow 2.6.31-17-server #54-Ubuntu SMP Thu Dec 10 18:06:56 UTC 2009 x86_64

To access official Ubuntu documentation, please visit:
http://help.ubuntu.com/

  System information as of Thu Feb 18 09:31:36 GMT 2010

  System load: 0.0                Memory usage: 51%   Processes:       96
  Usage of /:  1.3% of 194.04GB   Swap usage:   0%    Users logged in: 0

  Graph this data and manage this system at https://landscape.canonical.com/

18 packages can be updated.
13 updates are security updates.

Last login: Thu Feb 18 09:26:14 2010 from gate.example.com

root@yellow:~# ~#
The following connections are open:
  #2 client-session (t4 r0 i0/0 o0/0 fd 6/7 cfd -1)

root@yellow:~# netstat -lntp | grep 3142
root@yellow:~#

Is there a command, such as rsync, which can synchronise huge, sparse, files from one linux server to another?

It is very important that the destination file remains sparse. It may be longer (but not bigger) than the drive which contains it. Only changed blocks should be sent across the wire.

I have tried rsync, but got no joy. https://groups.google.com/forum/#!topic/mailing.unix.rsync/lPOScZgFE9M

If I write a programme to do this, am I just reinventing the wheel? http://www.finalcog.com/synchronise-block-devices

Thanks,

Chris.