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57

I have had very good results using tar, pigz (parallel gzip) and nc. Source machine: tar -cf - -C /path/of/small/files . | pigz | nc -l 9876 Destination machine: To extract: nc source_machine_ip 9876 | pigz -d | tar -xf - -C /put/stuff/here To keep archive: nc source_machine_ip 9876 > smallstuff.tar.gz If you want to see the transfer rate just ...


23

A connection time-out occurs when the DNS server doesn't respond at all, or does not respond in a timely fashion. The first can be simulated by simply blocking al traffic to your DNS server, on a Linux system for instance with: # iptables -I OUTPUT -p udp -d <iIP of DNS server> --dport 53 -j DROP Using DROP as the target means you won't even get ...


20

I'd stick to the rsync solution. Modern (3.0.0+) rsync uses incremental file list, so it does not have to build full list before transfer. So restarting it won't require you to do whole transfer again in case of trouble. Splitting the transfer per top or second level directory will optimize this even further. (I'd use rsync -a -P and add --compress if your ...


15

Set up a VPN (if its internet), create a virtual drive of some format on the remote server (make it ext4), mount it on the remote server, then mount that on the local server (using a block-level protocol like iSCSI), and use dd or another block-level tool to do the transfer. You can then copy the files off the virtual drive to the real (XFS) drive at your ...


12

What you need is a "black hole server". You can use blackhole.webpagetest.org (72.66.115.13) which will silently drop all requests. Why I suggest this over the other answers, is because the aforementioned server has been established for this sole purpose. Example: barend@shells:~$ dig example.com @72.66.115.13 ; <<>> DiG 9.10.3-P4-Debian <&...


10

nameserver 127.0.0.1 won't work as the default behaviour is already that. Instead, try using a non existing DNS. To make sure, you can do: nslookup example.com 192.0.2.10 If you get no response, then you can use 192.0.2.10 as your DNS server.


9

If the old server is being decommissioned and the files can be offline for a few minutes then it is often fastest to just pull the drives out the old box and cable them into the new server, mount them (back online now) and copy the files to the new servers native disks.


8

The number one way to increase the speed of the connection is to work with the internet service provider (ISP). If the physical link is 1 Mbps symmetrical with 100 ms latency to the server, you will not be able to accelerate that beyond 1 Mbps and 100 ms latency via software. You can add additional physical links to the connection increasing the overall ...


6

The kernel timeout only applies if the connection is orphaned. If the connection is still attached to a socket, the program that owns that socket is responsible for timing out the shutdown of the connection. Likely it has called shutdown and is waiting for the connection to shut down cleanly. The application can wait as long as it likes for the shutdown to ...


6

Virtio is a para-virtualized driver, which means the os and driver are aware that it's not a physical Device. The driver is really an API between the guest and the hypervisor so it's linkspeed is totally disconnect from any physical device or Ethernet standard. This is a good thing as this is faster than the hypervisor pretending to be a physical device and ...


6

Your 'when' column is telling me that ntp last chatted with those servers at best 40 minutes ago, yet your poll interval is 1024 seconds (~17 minutes). ntp does not seem to be running properly, which makes sense given your firewall configuration. You'll need an outbound and an inbound allow rule for UDP 123. The inbound is needed since UDP is stateless. ...


6

First off, check that your bottleneck is not the CPU required for encryption on your VPN. If your CPU is already maxed then no arrangement of spreading your traffic over multiple connections at the existing VPN server can help, though increasing the CPU resources available could. A major limitation on the speed of any TCP connection is from the combination ...


5

Should icfg-eth1 have been generated when I added the host-only local connection in virtualbox? No. Since you performed a minimal installation NetworkManager is not installed and so there's nothing on the system to detect new network interfaces and configure them for you. ifcfg-eth0 was created for you since the interface existed during installation. ...


5

Core is the overall max receive buffer, while tcp relates to just that protocol. As for the priority-question: It seems that the tcp-setting will take precendence over the common max setting, which is a bit confusing. Setting max has no effect on the current tcp setting (just tested on CentOS 5). A more correct description would have been: default_max - ...


5

Setting an upper limit for packet size was done for two reasons: ensure reliable transmission of the data (longer data are more susceptible to being corrupted and their CRC have lower changes of detecting/correcting the corruption); ensure that all Ethernet-compliant device have at least a 1500 byte buffer to send/receive packets. As you suggested, the ...


4

There are at least two ways to do this differently: Remote console (HP ILO, DELL DRAC, ...) allowing you access via its own NIC and its own IP, which is independant from the main OS settings. If you err you can just 'remotely take the console' and fix things. Set up a reboot to a safe working state on a timer. Make your changes, then kill the safety timer. ...


4

You didn't specify --send-only, so it has no way to know whether or not you're done receiving. If you want it to receive data too, then you'll have to tell it when you're done. If you don't want it to receive data, specify --send-only.


4

Today, for a relatively modern Linux distro I would initially try to use the ip command ip link show and then filter it's output to get a list of interfaces. You can also use ifconfig -a but newer releases of some distros are nolonger installing this by default. Similarly netstat -i may be useful. You can use the iwconfig command to determine if an ...


4

A wrong boardcast IP would not affect reachability of addresses outside the network/broadcast address range. However, IPs inside that range will be treated as locals and they will not be routed at all. In your specific case, this means that .96 - .255 IPs are not visible from your servers. However, all other IPs outside your local range (.0 - .255) can be ...


4

When you set your default policy to DROP and ACCEPT only what you need, this is clearly more secure than allowing everything by default and selectively DROP unwanted traffic types. This at least saves you from securing the services that are not meant to be accessed remotely (from outside your machine or your LAN). Your system is more secure when you expose ...


4

No, this is not possible in the sense of a "normal" CPU. You could use CUDA or a similar library if supported on your GPU chip, but that is not at all useful for general server tasks. However, most servers that are not designed for GPU computing have very weak GPUs and wouldn't offer any real benefit anyway.


4

ARP only works on the same LAN (layer-2 broadcast domain) because an ARP request is a broadcast. Broadcasts do not cross a layer-3 boundary. MAC addresses are layer-2 addresses, and they are only significant, or even seen, on the same layer-2 broadcast domain. A host wishing to send traffic to a different layer-3 network will send the traffic to the layer-2 ...


3

Try this script I wrote: #!/bin/bash # Purpose: # Detect Stale File handle and remove it # Script created: July 29, 2015 by Birgit Ducarroz # Last modification: -- # # Detect Stale file handle and write output into a variable and then into a file mounts=`df 2>&1 | grep 'Stale file handle' |awk '{print ""$2"" }' > NFS_stales.txt` # Remove : ‘ and ’...


3

You can do this using auditd; ask it to audit all calls to bind(2) and listen(2) -- the former so you can see what port is being bound to, and the latter to know when the listening starts.


3

DNS is designed to be a tree, where everything can be found by starting at the top and following pointers down. It's perfectly possible to set up such a tree of your own on your isolated network. If you set things up this way, everything will work normally, documentation will make sense and you will have the least amount of unpleasant surprises. From you ...


3

Use mbuffer and if it is on a secure network you can avoid the encryption step.


3

Have you considered sneakernet? With that, I mean transfering everything onto the same drive, then physically moving that drive over. about a month ago, Samsung unveiled a 16 TB drive (technically, it's 15.36 TB), which is also an SSD: http://www.theverge.com/2015/8/14/9153083/samsung-worlds-largest-hard-drive-16tb I think this drive would just about do ...


3

It means that a packet with a tweaked TTL did not return an appropriate ICMP TTL exceeded packet, or that those packets were lost on the way back, within the given period traceroute waits for them. This CAN mean, that the host on the way is not generating them properly if at all. There is little you can do about this. You can change the protocol traceroute ...


3

One, at least in that manner; --dport (on its own) doesn't take a list of ports. -m multiport enables the use of a list of ports, and that seems to be limited by a variable XT_MULTI_PORTS, which seems to be compiled-in at 15. A quick test suggests that 15 is indeed a limit: [root@risby ~]# iptables -A INPUT -p tcp -m multiport --dports 1,2,3,4,5,6,7,8,9,...


3

Actually, I think the confusion comes from the fact that those instructions are mixing two topics : Dealing with policy routing Setting up your standard routing table in a best-practice way These three lines ip route add $P1_NET dev $IF1 src $IP1 ip route add $P2_NET dev $IF2 src $IP2 ip route add default via $P1 are there to handle ...



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