Hot answers tagged

56

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 ...


42

Unplug the ethernet cable and see who gets upset. Seriously though, mystery machines like this create a lot of mental overhead for a team and often provide absolutely no business value. Talk to your boss, if no one knows what it does maybe no one cares what it does.


30

This is a pretty broad question for the Serverfault format, but here is a good start: Check for running processes and those scheduled to run at system startup. Review the running configuration of each. Look into any defined data directories. (Maybe someone installed MySQL and turned it on, but there are no databases.) Check for scheduled tasks. Check the ...


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 ...


19

There are a few things you could do to try and ascertain what's running on your system. You can check which ports your server is listening on to get an idea of what's on there. A good command to use would be: [root@server ~]# netstat -tulpn Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address ...


18

Another method involves checking the /etc directory and looking at the modification dates. After a fresh install all the files in this directory should have roughly the same date/time. And since an install usually installs a lot of things people usually do not use, only the files that have a later modification date reflect the actual purpose of the server. ...


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 ...


10

If you really need a quick way to transfer files, and both systems are Linux-based, you can try UDR. This is really a form of rsync-over-UDP (using the open-source UDT framework) and is particularly handy for moving large numbers of files or transferring over high-bandwidth or high-latency links. In addition, encryption is disabled by default, so the ...


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

You want eth1 and eth2 on the same subnet so they should be on the same ethernet link: you should configure your linux box as a bridge between eth1 and eth2. This will create a new network interface (named br0 below): the kernel will work as a switch bridging your eth1 and eth2 (at layer 2). The IP configuration will be done on br0 instead of eth1 and eth2 ...


8

In Centos7.0 disabling NetworkManager will leave a dhcp client running configured for NetworkManager. This causes the error message RTNETLINK answers: File exists when the network service is started. The stale dhclient process has the additional "benefit" that when the lease expires your dhclient will choke, since it cannot reach NetWorkManager, thus ...


7

I do exactly that. The test is pretty trivial, inasmuch as it connects to a custom database called nagios and selects from a table that contains just a single numeric value, alerting if that value isn't 74581 - but I figure if mysql works well enough to retrieve that exact number from a table, it's probably fine. You could run more complex queries, though. ...


7

Check the firewall rules. With a bit of luck, it's configured for default-deny. That means there's an explicit rule for each allowed service. This is better then netstat because it can also show ports that are open for e.g for nightly backups.


6

One answer I've not seen yet: Check the most recently modified files. Logs, database files, other output files etc. may get written to still that may provide clues: find . -mtime -3 That would find modified files in the current directory and deeper, changed in the last 3 days. Increase the number 3 to an educated guess until you get some output you can ...


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

Incoming connections are always going to match one of those rules aren't they? A connection from 10.51.0.1 for example won't get logged by the first rule but will hit the second one. Don't you need the equivalent of !10.51.0.0/16 && !192.168.0.0/16 (probably not valid syntax but correct logically).


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. ...


5

There is no charge for the Google Compute Engine ingress traffic. Take a look at GCE network pricing. If you've been charged for the ingress traffic, you can contact the Cloud billing team to clarify and fix the charge. Regarding the requests to port 11, as far as this port is blocked in your GCE network's firewall your VM instances should be safe and the ...


5

The subnet mask is mostly used to work out whether another IP address can be accessed on the local network, or if it needs to go through a router. Your workstations with the old /24 subnet mask will have been able to access everything else that was inside the old /24 network, because the wrong mask will still give the right answer for those addresses. They ...


4

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. ...


4

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 ...


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

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 - ...


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

Firewalls have two main choices when receiving unwanted connection attempts. REJECT - send a response saying the port/service/etc is closed or unavailable DROP - don't respond and just drop the packets The words REJECT/DROP aren't standard or used across all firewalls but the difference between the concepts behind the two possible actions will be ...


4

Just to explain why you need a bridge... A Bridge creates a link between two Layer 2 networks (eth1 and eth2 in your case) to act as a single Layer 2 network. This is Switching. A Router creates a link between two Layer 3 networks (eth0 and br0 in your case once you create the bridge). This is routing. With both clients in the same subnet, there is no ...


4

Long waiting for SMTP greeting How long do you wait to get SMTP greeting message? Exact duration in seconds may provide very important hint. AFAIR some servers issue SMTP greeting message after doing DNS lookups (IP address -> DNS name -> IP address). Typical timeout for single DNS query is 75s. DNS is not the only suspect (e.g. ident timeout may be ...


4

TL;DR but... Pure port range without multiport module: iptables -A INPUT -p tcp --dport 1000:2000 -j ACCEPT Equivalent multiport example: iptables -A INPUT -p tcp -m multiport --dports 1000:2000 -j ACCEPT ...and variation about multi port with multi ranges (yes, this is also possible): iptables -A INPUT -p tcp -m multiport --dports ...


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 ...



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