I have several applications which works together and need to communicate.
These applications can be installed on different host, which can be in different local networks, but all are connected together via a global network.
The host can be Linux (CenOS, Debian, Ubuntu) or Windows (7/10).
Now, I need to identify which host is running an application.
The requirements are :
- every application running on the same host have the same "host ID"
- every "host ID" is unique among all hosts
Since the host can be physical machines, virtual machines or even docker instances, I don't think I can use the hostname as a "global unique ID".
Since the host can be in different local networks, I don't think I can use local IP address as a "global unique ID".
So, which data can I use ? Maybe the Network adapter MAC address ? Is it
guaranteed to be unique, even between multiple instances of the same docker ?
Thanks.
On modern / recent Linux distro, linux generates for you a unique id in the /etc/machine-id file when the system is created the first time. Some distributed services such as etcd rely on this file to identify machines in a cluster.
Nothing prevents you from creating and persisting on disk something like a uuid. You can use uuidgen command on Linux for that.
You can say the MAC address is unique. However, if you are concerned about security, do not use the MAC address. The MAC address can be spoofed easily.
To generate a unique ID for the machine, you can use a combination of many items such as MAC Address, IP Address, hostname etc., throw in a random salt and take a sha256 hash of them. Since the host can run on many operating system, I would suggest against using any OS-specific parameters.
Without going into too much detail, the chances of finding a collision in sha256 is improbable to say the least.
You can see the SHA256 of different text here.
http://www.xorbin.com/tools/sha256-hash-calculator
Almost every programming language, these days, has a function/API for creating a SHA256 hash.
Looks like /var/lib/dbus/machine-id contains what you need.
read more here: http://man7.org/linux/man-pages/man5/machine-id.5.html
On linux I solved my problem just by changing the contents of the /var/lib/dbus/machine-id file
Related
I am trying to identify computers with a unique code based on their machine. However, I can't find any way to do this. I've tried to use mac addresses, but you can only the server's mac address when you're using a linux server. I would use the clients ip address, but it can change if they're using a proxy or vpn, or even if they just unplug their router for a bit.
Can anyone recommend something that would be good for this?
Thanks.
There is no secure way to uniquely identify computers based on hardware, and why should you?
The better practice would be to use an artificial key.
If you want to identify a person - you give it an ID (passport, driving license...), do the same here:
Use the session (apache generates automatically a session ID), or generate a UUID (there are many ways to do this). Or if you need to go beyond - use ssh key pairs, save them somewhere on the PC.
Now to the problem:
1. A client could lie about his hardware, his mac address, VIN/PID, serial number of the SATA cable. You can (and must) never trust such info!
2. Clients hardware could change, and then?
My python application running as a daemon in a variety of linux distributions are trying to register to my server using the machine's IP Address and FQDN Hostname(given by "hostname -f" command) as a primary key.
Now I am facing a problem when two machines are having same hostname and IP Address. Eg in case of two VM's running on two seperate machines, the hostname is "localhost.localdomain" and Ip Address is "192.168.0.2" for both of them.
Is there any unique way to differentitate any two machines. (Maybe some other third parameter which will guarantee uniqueness across any linux machine )
the MAC address should be unique per network interface.
maybe you can try a combination of IP, MAC and host name?
another option is to create a UUID and save it on the machine.
I am working in PHP. I need a computer dependent login system. I mean to say that a user cannot login using multiple computer it will be restricted to only one machine. If so, I will need administrator to handle this case. I tried to make this IP dependent, but I saw that in a network I can login with all computers as they are sharing the same internet connection.
You can try to get the MAC Address which is unique for every machine and is given by the Constructor of the machine.
PS:
#Emmanuel: You can have the same computer name on two machines.
UPDATE:
Some links form getting MAC address in PHP:
http://nazmulb.wordpress.com/2008/07/04/getting-mac-address-using-php/
http://forums.techarena.in/software-development/1179119.htm
I'm setting up a linux server in a VM for my development.
Previously I've had PHP, MySQL etc etc all installed locally on my Mac. Apart from being a security risk, it's a drag to maintain and keep up to date, and there's a risk that an OS upgrade will wipe part of your setup out as the changes you make are fairly non-standard.
Having the entire server contained within a VM makes it easily upgradable and portable between machines. It means I can have the same configuration as the destination server and with shared folders even if the VM gets corrupted my work is safe on the host machine.
Previously with the local installation I was able to develop on convenient URLs like http://site.dev. I'd quite like to carry this over to the VM way of development but I'm struggling to figure out how, if it's possible at all.
Here's the problem:
In Bridged mode, the VM is part of the same network as the host. This is great but I can't choose a fixed IP address as I may be joining other networks and that address may be taken already. I'd like a consistent way of addressing my VM.
In NAT mode I can't directly address the VM without using port forwarding. I can use http://site.dev if I use the hosts file to forward that to localhost and then localhost:8080 forwards to the vm:80. The trouble is I have to access http://site.dev:8080 which is inconvenient for URL construction.
Does anyone know a way around this? I'm using ubuntu server and virtualbox.
Thanks!
The answer is to define a separate host-only network adapter and use that for host->guest communication.
You can do this by powering down the guest and adding the adapter in the VM settings. Once that's done you can boot the guest again and configure the new network interface however suits you best. I chose a fixed IP address in an unused range.
I need to store persistent reference to third party device on an arbitrary IP network where the IP address of the devices may be static or randomly assigned by DHCP. I don't control the devices on the network and I can't rely on DNS and other ad-hoc networking protocols existing or working with the devices.
So I have been instructed to investigate using hardware addresses and ARP. This will work but I don't want to duplicate code. The kernel must manage an ARP table. On Windows you can access it using GetIpNetTable etc.
I am hoping there is an API to answer these two questions:
How do I translate from IP to MAC address? (ARP)
How do I translate from MAC to IP address? (InARP)
If not then I may have to do it more manually:
How do I read the kernel's ARP table?
How do I add an entry if I have the determined a mapping myself?
/proc/net/arp
K
ARP tables tend to be fairly local and short-lived. If you examine the protocol, the real MAC addresses are generally only provided when the given IP address is in the local subnet.
Otherwise, the packet is forwarded to the local router, which is then responsible for forwarding it.
If you do "arp -g" on Windows or "arp -a" on UNIX, you'll see the table, but I don't think it will do you any good, due to the reasons mentioned above. That command and
That's really what DNS is for but, as you say, it may not be an option for you.
You may well have to write your own 'ARP' database at your application level.
As for ARP:
You could use system("/usr/bin/arp -option_of_choice"); and parse the output, but that's an ugly hack. -- Not my recommendation.
Take a look at /usr/include/linux/sockios.h -- At the SIOCGARP, SIOCDARP, and SIOCSARP details. Those are ioctls that you can perform to manage the ARP table on linux. Of course, you'll have to perform these ioctls on a socket fd.
Here's some examples: SIOCGARP examples
I'm sure you can find many other examples in several other languages as well. As I'm assuming that you're using C.
As for RARP:
A quote from the linux rarp manpage:
" This program is obsolete. From version 2.3, the Linux kernel no longer
contains RARP support. For a replacement RARP daemon, see ftp://ftp.demen-
tia.org/pub/net-tools"
So you'll have to install rarpd on the target system.