Hi, I would like to set the hostname when installing a guest, with the below command the hostname is not set to 'try06' in the guest: virt-install --name=try06 --graphic none --pxe --network bridge=virbr0

On 27. 3. 2020 16:48, Michal Prívozník wrote: > On 27. 3. 2020 14:57, john doe wrote: >> Hi, >> >> I would like to set the hostname when installing a guest, with the below >> command the hostname is not set to 'try06' in the guest: >> >> virt-install --name=try06 --graphic none --pxe --network bridge=virbr0 > > This is the name of the guest registered in libvirt. I don't think that > virt-install has wired up setting hostname, but it looks like it can do > it. I mean, use --name for both libvirt name and guest hostname. On the other hand, users might want to set it to something else. So we really should have a separate argument for that. Anyway, I've reported it to virt-install developers: https://github.com/virt-manager/virt-manager/issues/94

On 27. 3. 2020 17:23, john doe wrote: > On 3/27/2020 5:13 PM, Michal Prívozník wrote: >> On 27. 3. 2020 16:48, Michal Prívozník wrote: >>> On 27. 3. 2020 14:57, john doe wrote: >>>> Hi, >>>> >>>> I would like to set the hostname when installing a guest, with the below >>>> command the hostname is not set to 'try06' in the guest: >>>> >>>> virt-install --name=try06 --graphic none --pxe --network bridge=virbr0 >>> >>> This is the name of the guest registered in libvirt. I don't think that >>> virt-install has wired up setting hostname, but it looks like it can do >>> it. I mean, use --name for both libvirt name and guest hostname. >> >> On the other hand, users might want to set it to something else. So we >> really should have a separate argument for that. Anyway, I've reported >> it to virt-install developers: >> >> https://github.com/virt-manager/virt-manager/issues/94 >> > > Many thanks for your answer and for passing it along. > > I agree, an option to trigger this behavior is best. > > After executing the above command and before the hostname step, the > following workaround seems to work: > > $ virsh net-dhcp-leases default > Expiry Time MAC address Protocol IP address > Hostname Client ID or DUID > ----------------------------------------------------------------------------------------------------------------------------------------------- > 2020-03-27 18:03:36 52:54:00:9d:d1:e7 ipv4 192.168.122.45/24 > - ff:00:9d:d1:e7:00:01:00:01:26:10:e0:58:52:54:00:9d:d1:e7 > > $ virsh net-update default add ip-dhcp-host "<host > mac='52:54:00:9d:d1:e7' name='try06' ip='192.168.122.45'/>" > > > What I am not sure about is how to predetermine the MAC address of the > guest before starting the installer? You can switch the steps and generate a MAC address yourself, then update the network and then specify it on virt-install cmd line. Or even better, do not bother with any of this and use libvirt-nss plugin: https://libvirt.org/nss.html

On 27. 3. 2020 19:23, john doe wrote: > Okay, I have installed the pluging, do you mind explaning how this > should work?: > > $ grep host /etc/ns* > hosts: files libvirt_guest dns > > > If I'm correct, following your example, I should be able to do: > > $ host try06 > > What am I missing. 'host' does DNS directly, regardless of nsswitch.conf. That's not how majority of SW work. Try: getent hosts try06 or: ssh try06 The majority will use gethostbyname() which will consult the nsswitch.conf and use modules defined there. In your case, the /etc/hosts will be consulted first, then libvirt_guest and DNS is used only if everything else failed. You can verify that 'host' does DNS directly by trying a hostname from /etc/hosts. It will give an error even though getent won't. Michal

On 3/27/2020 8:29 PM, john doe wrote: > On 3/27/2020 7:36 PM, Michal Prívozník wrote: >> On 27. 3. 2020 19:23, john doe wrote: >>> Okay, I have installed the pluging, do you mind explaning how this >>> should work?: >>> >>> $ grep host /etc/ns* >>> hosts: files libvirt_guest dns >>> >>> >>> If I'm correct, following your example, I should be able to do: >>> >>> $ host try06 >>> >>> What am I missing. >> >> 'host' does DNS directly, regardless of nsswitch.conf. That's not how >> majority of SW work. Try: >> >> getent hosts try06 >> >> or: >> >> ssh try06 >> >> The majority will use gethostbyname() which will consult the >> nsswitch.conf and use modules defined there. In your case, the >> /etc/hosts will be consulted first, then libvirt_guest and DNS is used >> only if everything else failed. You can verify that 'host' does DNS >> directly by trying a hostname from /etc/hosts. It will give an error >> even though getent won't. >> >> Michal >> > > Thanks for the explanation but it does not seem to work: > > $ getent hosts try06; echo $? > 2 > > > Using 'libvirt' or libvirt_guest' one or the other or both does not > change the above, for testing purposes the line 'hosts: ...' has only > libvirt modules. > > It is also not working for SSH. > > Testing this on Debian Buster (10) ('libnss-libvirt is already the > newest version (5.0.0-4+deb10u1)'). > > Your help is appriciated. > With some more testing: $ grep hosts: /etc/ns* hosts: file libvirt libvirt_guest dns $ virsh net-dhcp-leases default Expiry Time MAC address Protocol IP address Hostname Client ID or DUID ------------------------------------------------------------------------------------------------------------------------------------------------ 2020-03-27 21:40:49 52:54:00:d4:e6:f0 ipv4 192.168.122.137/24 debian ff:00:d4:e6:f0:00:01:00:01:26:11:0b:0c:52:54:00:d4:e6:f0 $ getent hosts try06 $ getent hosts debian 192.168.122.137 debian

If my understanding is correct, using 'try06' or 'debian' should do the same thing?

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

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

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 <network> 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 <network> 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     01:52:54:00:a4:6f:91

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 <network> 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.

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: >> >>> >>>> 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 <network> 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.

On 3/27/2020 5:13 PM, Michal Prívozník wrote: > On 27. 3. 2020 16:48, Michal Prívozník wrote: >> On 27. 3. 2020 14:57, john doe wrote: >>> Hi, >>> >>> I would like to set the hostname when installing a guest, with the >>> below >>> command the hostname is not set to 'try06' in the guest: >>> >>> virt-install --name=try06 --graphic none --pxe --network bridge=virbr0 >> >> This is the name of the guest registered in libvirt. I don't think that >> virt-install has wired up setting hostname, but it looks like it can do >> it. I mean, use --name for both libvirt name and guest hostname. > > On the other hand, users might want to set it to something else. So we > really should have a separate argument for that. Anyway, I've reported > it to virt-install developers: > > https://github.com/virt-manager/virt-manager/issues/94 > Hi, This bug is now RFI, is there anything that I can do to move it along?

Will this option be of any help if installing a VM using PXE?

On 27. 3. 2020 14:57, john doe wrote: > Hi, > > I would like to set the hostname when installing a guest, with the below > command the hostname is not set to 'try06' in the guest: > > virt-install --name=try06 --graphic none --pxe --network bridge=virbr0 This is the name of the guest registered in libvirt. I don't think that virt-install has wired up setting hostname, but it looks like it can do it. I mean, use --name for both libvirt name and guest hostname.