Re: Set hostname of guest during installation time
On 5/5/20 11:25 AM, john doe wrote: On 5/5/2020 10:41 AM, Michal Privoznik wrote: On 5/5/20 9:26 AM, john doe wrote: On 5/5/2020 8:29 AM, Michal Privoznik wrote: Because interface type='bridge' and type='network' are not the same. The libvirt_guest plugin needs a list of MAC addresses because it tries to find a match across libvirt domain name -> list of domain's MAC addresses -> list of leases. And whenever a domain is started, all its interfaces with type='network' will notify the corresponding network and the code that handles libvirt networks will dump the MAC address into a file for the NSS plugin to use. But, if plain type='bridge' is used then all that is done is that the TAP is plugged into the bridge (which ensures the connectivity), but does not notify the network which in turn means that the MAC dumping code is not run and hence the NSS plugin won't find a match. I don't understand why the network can not be notified, could it be a feature request? No. interface type='bridge' exists exactly for the reasons that users want libvirt just to plug TAP device into a bridge they manage. And they don't want libvirt to touch the bridge in any other way. Is there a reason why you are using interface type='bridge' with the default network? I'm just starting with libvirt, so I could be missing something. Yes, I don't need libvirt touching iptables at all. In other words, is there a way to be able to use libvirt_guest without having libvirt interacting with iptables. I'm not quite sure how to achieve NAT then - do you insert the NAT rules yourself? Yes, my frontent to iptables will do that. If it is so, then what you may do is to change the type of the default network to 'open' and then use interface type='network' from the domain. Thank you, I'll need to look into that. Is there a way to do that with virt-install? Let me check the man page for you. --network network=my_libvirt_virtual_net Also, from (1): "virsh net-dhcp-leases $network where $network iterates through all running network..." If I understand correctly, the below should list all running network: $ virsh net-dhcp-leases $network error: command 'net-dhcp-leases' requires option This lists DHCP leases for given network. To list all running networks you can use 'virsh net-list'. I would suggest rephrasing the above to something along the lines of: "virsh net-dhcp-leases $network, where '$network' is to be supstituted by the desired network (E.G, 'default') or use virsh net-list to list all available network." Actually, the whole statement (copied verbatim from the webpage) is: The NSS module then merely consults the list trying to find the match. Users can view the list themselves: virsh net-dhcp-leases $network where $network iterates through all running networks. '$network iterates through all running networks.' I don't understand what 'all networks' refers to? Just like there can be multiple domains running there can be multiple networks. Maybe I'm assuming too much, but this doesn't say that net-dhcp-leases will print all running networks. The way I read this is: The NSS module then merely does equivalent of iterating over every running network and executing 'net-dhcp-leases' and trying to find the match. I thought that using shell variables in a documentation for an UNIX-like command is well understood, but maybe I am wrong. That is the first time that I see this syntax being used, simply adding somewhere that when an example for a command is shown like so, this should be substituted. Our docs are kept in a repository. In this specific example it is docs/nss.html.in: https://gitlab.com/libvirt/libvirt/-/blob/master/docs/nss.html.in If you feel like our docs are misleading, please post a patch. Michal
Re: Set hostname of guest during installation time
On 5/5/2020 10:41 AM, Michal Privoznik wrote: On 5/5/20 9:26 AM, john doe wrote: On 5/5/2020 8:29 AM, Michal Privoznik wrote: Because interface type='bridge' and type='network' are not the same. The libvirt_guest plugin needs a list of MAC addresses because it tries to find a match across libvirt domain name -> list of domain's MAC addresses -> list of leases. And whenever a domain is started, all its interfaces with type='network' will notify the corresponding network and the code that handles libvirt networks will dump the MAC address into a file for the NSS plugin to use. But, if plain type='bridge' is used then all that is done is that the TAP is plugged into the bridge (which ensures the connectivity), but does not notify the network which in turn means that the MAC dumping code is not run and hence the NSS plugin won't find a match. I don't understand why the network can not be notified, could it be a feature request? No. interface type='bridge' exists exactly for the reasons that users want libvirt just to plug TAP device into a bridge they manage. And they don't want libvirt to touch the bridge in any other way. Is there a reason why you are using interface type='bridge' with the default network? I'm just starting with libvirt, so I could be missing something. Yes, I don't need libvirt touching iptables at all. In other words, is there a way to be able to use libvirt_guest without having libvirt interacting with iptables. I'm not quite sure how to achieve NAT then - do you insert the NAT rules yourself? Yes, my frontent to iptables will do that. If it is so, then what you may do is to change the type of the default network to 'open' and then use interface type='network' from the domain. Thank you, I'll need to look into that. Is there a way to do that with virt-install? Also, from (1): "virsh net-dhcp-leases $network where $network iterates through all running network..." If I understand correctly, the below should list all running network: $ virsh net-dhcp-leases $network error: command 'net-dhcp-leases' requires option This lists DHCP leases for given network. To list all running networks you can use 'virsh net-list'. I would suggest rephrasing the above to something along the lines of: "virsh net-dhcp-leases $network, where '$network' is to be supstituted by the desired network (E.G, 'default') or use virsh net-list to list all available network." Actually, the whole statement (copied verbatim from the webpage) is: The NSS module then merely consults the list trying to find the match. Users can view the list themselves: virsh net-dhcp-leases $network where $network iterates through all running networks. '$network iterates through all running networks.' I don't understand what 'all networks' refers to? Maybe I'm assuming too much, but this doesn't say that net-dhcp-leases will print all running networks. The way I read this is: The NSS module then merely does equivalent of iterating over every running network and executing 'net-dhcp-leases' and trying to find the match. I thought that using shell variables in a documentation for an UNIX-like command is well understood, but maybe I am wrong. That is the first time that I see this syntax being used, simply adding somewhere that when an example for a command is shown like so, this should be substituted. -- John Doe
Re: Set hostname of guest during installation time
On 5/5/20 9:26 AM, john doe wrote: On 5/5/2020 8:29 AM, Michal Privoznik wrote: Because interface type='bridge' and type='network' are not the same. The libvirt_guest plugin needs a list of MAC addresses because it tries to find a match across libvirt domain name -> list of domain's MAC addresses -> list of leases. And whenever a domain is started, all its interfaces with type='network' will notify the corresponding network and the code that handles libvirt networks will dump the MAC address into a file for the NSS plugin to use. But, if plain type='bridge' is used then all that is done is that the TAP is plugged into the bridge (which ensures the connectivity), but does not notify the network which in turn means that the MAC dumping code is not run and hence the NSS plugin won't find a match. I don't understand why the network can not be notified, could it be a feature request? No. interface type='bridge' exists exactly for the reasons that users want libvirt just to plug TAP device into a bridge they manage. And they don't want libvirt to touch the bridge in any other way. Is there a reason why you are using interface type='bridge' with the default network? I'm just starting with libvirt, so I could be missing something. Yes, I don't need libvirt touching iptables at all. In other words, is there a way to be able to use libvirt_guest without having libvirt interacting with iptables. I'm not quite sure how to achieve NAT then - do you insert the NAT rules yourself? If it is so, then what you may do is to change the type of the default network to 'open' and then use interface type='network' from the domain. Also, from (1): "virsh net-dhcp-leases $network where $network iterates through all running network..." If I understand correctly, the below should list all running network: $ virsh net-dhcp-leases $network error: command 'net-dhcp-leases' requires option This lists DHCP leases for given network. To list all running networks you can use 'virsh net-list'. I would suggest rephrasing the above to something along the lines of: "virsh net-dhcp-leases $network, where '$network' is to be supstituted by the desired network (E.G, 'default') or use virsh net-list to list all available network." Actually, the whole statement (copied verbatim from the webpage) is: The NSS module then merely consults the list trying to find the match. Users can view the list themselves: virsh net-dhcp-leases $network where $network iterates through all running networks. Maybe I'm assuming too much, but this doesn't say that net-dhcp-leases will print all running networks. The way I read this is: The NSS module then merely does equivalent of iterating over every running network and executing 'net-dhcp-leases' and trying to find the match. I thought that using shell variables in a documentation for an UNIX-like command is well understood, but maybe I am wrong. Michal
Re: Set hostname of guest during installation time
On 5/5/2020 8:29 AM, Michal Privoznik wrote: On 5/5/20 8:11 AM, john doe wrote: On 3/30/2020 4:10 PM, Michal Prívozník wrote: On 30. 3. 2020 15:26, john doe wrote: On 3/30/2020 1:20 PM, Andrea Bolognani wrote: On Mon, 2020-03-30 at 12:04 +0200, Michal Prívozník wrote: On 27. 3. 2020 20:49, john doe wrote: If my understanding is correct, using 'try06' or 'debian' should do the same thing? Yes, that is the idea. However, these plugins were not introduced at the same time. I think that especially Debian has delayed libvirt_guest plugin. You can check if both plugins exist: ls /usr/lib64/libnss_libvirt* /usr/lib64/libnss_libvirt_guest.so.2 /usr/lib64/libnss_libvirt.so.2 Note that paths are different in Debian-based distros, so the correct ones in this case are actually /lib/x86_64-linux-gnu/libnss_libvirt.so.2 /lib/x86_64-linux-gnu/libnss_libvirt_guest.so.2 I have upgraded that Buster host to Bullseye, so I have now a 6... version. I have also the above two modules. I'm still not able to use 'libvirt_guest' though: --- Guest output (try06): root@try06:~# cat /etc/hostname try06 --- Host output (host): root@host:# grep hosts: /etc/ns* hosts: libvirt_guest root@host:# virsh net-dhcp-leases default Expiry Time MAC address Protocol IP address Hostname Client ID or DUID - 2020-03-30 16:03:41 52:54:00:d4:e6:f0 ipv4 192.168.122.137/24 - - root@host:# getent hosts try06; echo $? 2 What am I missing? Hold on. 'libvirt_guest' NSS plugin is supposed to translate libvirt names to IP addresses. For instance: virsh start myDomain; ssh myDomain The 'libvirt' NSS plugin is supposed to translate hostnames as sent by guests to IP addresses. These two can be viewed as the following: libvirt_guest: virsh domifaddr --source lease $dom libvirt: virsh net-dhcp-leases $net | grep $hostname And this is where it gets interesting. In your previous e-mails, net-dhcp-leases (aka 'libvirt' plugin) worked because the guest did send hostname when doing DHCP. Now it doesn't (see '-' under 'Hostname' in the output). Therefore, the 'libvirt' NSS plugin won't work. And 'libvirt_guest' translates names of guests as seen by libvirt, i.e. names you pass to virsh commands. These are unrelated to '/etc/hostname' within guest. But hopefully, you haven't renamed your guest since then and it is still named 'try06', that is virsh list --all produces 'try06' in the list. If this is all true, can you share the output of: strace $(which getent) hosts try06 Thanks to the friendly feedback/support from Michal Privoznik and Andrea Bolognani, I managed to get it working with the below command: virt-install --name=try06 --pxe --os-variant=debian10 --network network=default What I think I mist while trying to implement the recommendation given in here is that, if you change the network by doing 'virsh edit default' the name of the interface in the guest might also change. I don't understand why libvirt_guest won't work if a network bridge is used? Because interface type='bridge' and type='network' are not the same. The libvirt_guest plugin needs a list of MAC addresses because it tries to find a match across libvirt domain name -> list of domain's MAC addresses -> list of leases. And whenever a domain is started, all its interfaces with type='network' will notify the corresponding network and the code that handles libvirt networks will dump the MAC address into a file for the NSS plugin to use. But, if plain type='bridge' is used then all that is done is that the TAP is plugged into the bridge (which ensures the connectivity), but does not notify the network which in turn means that the MAC dumping code is not run and hence the NSS plugin won't find a match. I don't understand why the network can not be notified, could it be a feature request? Is there a reason why you are using interface type='bridge' with the default network? I'm just starting with libvirt, so I could be missing something. Yes, I don't need libvirt touching iptables at all. In other words, is there a way to be able to use libvirt_guest without having libvirt interacting with iptables. Also, from (1): "virsh net-dhcp-leases $network where $network iterates through all running network..." If I understand correctly, the below should list all running network: $ virsh net-dhcp-leases $network error: command 'net-dhcp-leases' requires option This lists DHCP leases for given network. To list all running networks you can use 'virsh net-list'. I would suggest rephrasing the above to something along the lines of: "virsh net-dhcp-leases $network, where '$network' is to be supstituted by the desired network (E.G, 'default') or use virsh net-list to list all available network." In my case, I substituted '$network' by 'default'. It doesn't look like you did,
Re: Set hostname of guest during installation time
On 5/5/20 8:11 AM, john doe wrote: On 3/30/2020 4:10 PM, Michal Prívozník wrote: On 30. 3. 2020 15:26, john doe wrote: On 3/30/2020 1:20 PM, Andrea Bolognani wrote: On Mon, 2020-03-30 at 12:04 +0200, Michal Prívozník wrote: On 27. 3. 2020 20:49, john doe wrote: If my understanding is correct, using 'try06' or 'debian' should do the same thing? Yes, that is the idea. However, these plugins were not introduced at the same time. I think that especially Debian has delayed libvirt_guest plugin. You can check if both plugins exist: ls /usr/lib64/libnss_libvirt* /usr/lib64/libnss_libvirt_guest.so.2 /usr/lib64/libnss_libvirt.so.2 Note that paths are different in Debian-based distros, so the correct ones in this case are actually /lib/x86_64-linux-gnu/libnss_libvirt.so.2 /lib/x86_64-linux-gnu/libnss_libvirt_guest.so.2 I have upgraded that Buster host to Bullseye, so I have now a 6... version. I have also the above two modules. I'm still not able to use 'libvirt_guest' though: --- Guest output (try06): root@try06:~# cat /etc/hostname try06 --- Host output (host): root@host:# grep hosts: /etc/ns* hosts: libvirt_guest root@host:# virsh net-dhcp-leases default Expiry Time MAC address Protocol IP address Hostname Client ID or DUID - 2020-03-30 16:03:41 52:54:00:d4:e6:f0 ipv4 192.168.122.137/24 - - root@host:# getent hosts try06; echo $? 2 What am I missing? Hold on. 'libvirt_guest' NSS plugin is supposed to translate libvirt names to IP addresses. For instance: virsh start myDomain; ssh myDomain The 'libvirt' NSS plugin is supposed to translate hostnames as sent by guests to IP addresses. These two can be viewed as the following: libvirt_guest: virsh domifaddr --source lease $dom libvirt: virsh net-dhcp-leases $net | grep $hostname And this is where it gets interesting. In your previous e-mails, net-dhcp-leases (aka 'libvirt' plugin) worked because the guest did send hostname when doing DHCP. Now it doesn't (see '-' under 'Hostname' in the output). Therefore, the 'libvirt' NSS plugin won't work. And 'libvirt_guest' translates names of guests as seen by libvirt, i.e. names you pass to virsh commands. These are unrelated to '/etc/hostname' within guest. But hopefully, you haven't renamed your guest since then and it is still named 'try06', that is virsh list --all produces 'try06' in the list. If this is all true, can you share the output of: strace $(which getent) hosts try06 Thanks to the friendly feedback/support from Michal Privoznik and Andrea Bolognani, I managed to get it working with the below command: virt-install --name=try06 --pxe --os-variant=debian10 --network network=default What I think I mist while trying to implement the recommendation given in here is that, if you change the network by doing 'virsh edit default' the name of the interface in the guest might also change. I don't understand why libvirt_guest won't work if a network bridge is used? Because interface type='bridge' and type='network' are not the same. The libvirt_guest plugin needs a list of MAC addresses because it tries to find a match across libvirt domain name -> list of domain's MAC addresses -> list of leases. And whenever a domain is started, all its interfaces with type='network' will notify the corresponding network and the code that handles libvirt networks will dump the MAC address into a file for the NSS plugin to use. But, if plain type='bridge' is used then all that is done is that the TAP is plugged into the bridge (which ensures the connectivity), but does not notify the network which in turn means that the MAC dumping code is not run and hence the NSS plugin won't find a match. Is there a reason why you are using interface type='bridge' with the default network? Also, from (1): "virsh net-dhcp-leases $network where $network iterates through all running network..." If I understand correctly, the below should list all running network: $ virsh net-dhcp-leases $network error: command 'net-dhcp-leases' requires option This lists DHCP leases for given network. To list all running networks you can use 'virsh net-list'. In my case, I substituted '$network' by 'default'. It doesn't look like you did, otherwise you would either get leases or an error that there is no network named "default". # virsh net-dhcp-leases error: command 'net-dhcp-leases' requires option # virsh net-dhcp-leases "" error: Failed to get option 'network': Option argument is empty # virsh net-dhcp-leases default Expiry Time MAC address Protocol IP address Hostname Client ID or DUID -- 2020-05-05 09:01:11 52:54:00:a4:6f:91 ipv4 192.168.122.3/24 fedora
Re: Set hostname of guest during installation time
On 3/30/2020 4:10 PM, Michal Prívozník wrote: On 30. 3. 2020 15:26, john doe wrote: On 3/30/2020 1:20 PM, Andrea Bolognani wrote: On Mon, 2020-03-30 at 12:04 +0200, Michal Prívozník wrote: On 27. 3. 2020 20:49, john doe wrote: If my understanding is correct, using 'try06' or 'debian' should do the same thing? Yes, that is the idea. However, these plugins were not introduced at the same time. I think that especially Debian has delayed libvirt_guest plugin. You can check if both plugins exist: ls /usr/lib64/libnss_libvirt* /usr/lib64/libnss_libvirt_guest.so.2 /usr/lib64/libnss_libvirt.so.2 Note that paths are different in Debian-based distros, so the correct ones in this case are actually /lib/x86_64-linux-gnu/libnss_libvirt.so.2 /lib/x86_64-linux-gnu/libnss_libvirt_guest.so.2 I have upgraded that Buster host to Bullseye, so I have now a 6... version. I have also the above two modules. I'm still not able to use 'libvirt_guest' though: --- Guest output (try06): root@try06:~# cat /etc/hostname try06 --- Host output (host): root@host:# grep hosts: /etc/ns* hosts: libvirt_guest root@host:# virsh net-dhcp-leases default Expiry Time MAC address Protocol IP address Hostname Client ID or DUID - 2020-03-30 16:03:41 52:54:00:d4:e6:f0 ipv4 192.168.122.137/24 - - root@host:# getent hosts try06; echo $? 2 What am I missing? Hold on. 'libvirt_guest' NSS plugin is supposed to translate libvirt names to IP addresses. For instance: virsh start myDomain; ssh myDomain The 'libvirt' NSS plugin is supposed to translate hostnames as sent by guests to IP addresses. These two can be viewed as the following: libvirt_guest: virsh domifaddr --source lease $dom libvirt: virsh net-dhcp-leases $net | grep $hostname And this is where it gets interesting. In your previous e-mails, net-dhcp-leases (aka 'libvirt' plugin) worked because the guest did send hostname when doing DHCP. Now it doesn't (see '-' under 'Hostname' in the output). Therefore, the 'libvirt' NSS plugin won't work. And 'libvirt_guest' translates names of guests as seen by libvirt, i.e. names you pass to virsh commands. These are unrelated to '/etc/hostname' within guest. But hopefully, you haven't renamed your guest since then and it is still named 'try06', that is virsh list --all produces 'try06' in the list. If this is all true, can you share the output of: strace $(which getent) hosts try06 Thanks to the friendly feedback/support from Michal Privoznik and Andrea Bolognani, I managed to get it working with the below command: virt-install --name=try06 --pxe --os-variant=debian10 --network network=default What I think I mist while trying to implement the recommendation given in here is that, if you change the network by doing 'virsh edit default' the name of the interface in the guest might also change. I don't understand why libvirt_guest won't work if a network bridge is used? Also, from (1): "virsh net-dhcp-leases $network where $network iterates through all running network..." If I understand correctly, the below should list all running network: $ virsh net-dhcp-leases $network error: command 'net-dhcp-leases' requires option In my case, I substituted '$network' by 'default'. 1) https://libvirt.org/nss.html#Internals -- John Doe
