9p (libvirt/QEMU) share modes












2















Can anybody explain what share modes - default, mapped, passthough, squashed - mean in libvirt/QEMU configuration?



enter image description here



I've got this share in passthrough mode. I see that inside VM it is owned by vagrant:vagrant user (which is absent from host machine) and share has rw bits set. But trying to create files there gives access denied error.



I need to understand what is going on to resolve the issue.










share|improve this question



























    2















    Can anybody explain what share modes - default, mapped, passthough, squashed - mean in libvirt/QEMU configuration?



    enter image description here



    I've got this share in passthrough mode. I see that inside VM it is owned by vagrant:vagrant user (which is absent from host machine) and share has rw bits set. But trying to create files there gives access denied error.



    I need to understand what is going on to resolve the issue.










    share|improve this question

























      2












      2








      2








      Can anybody explain what share modes - default, mapped, passthough, squashed - mean in libvirt/QEMU configuration?



      enter image description here



      I've got this share in passthrough mode. I see that inside VM it is owned by vagrant:vagrant user (which is absent from host machine) and share has rw bits set. But trying to create files there gives access denied error.



      I need to understand what is going on to resolve the issue.










      share|improve this question














      Can anybody explain what share modes - default, mapped, passthough, squashed - mean in libvirt/QEMU configuration?



      enter image description here



      I've got this share in passthrough mode. I see that inside VM it is owned by vagrant:vagrant user (which is absent from host machine) and share has rw bits set. But trying to create files there gives access denied error.



      I need to understand what is going on to resolve the issue.







      virtualization shared-folders qemu






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked May 15 '16 at 14:30









      anatoly techtonikanatoly techtonik

      82421431




      82421431






















          2 Answers
          2






          active

          oldest

          votes


















          2














          I once had a very similar problem, providing read-write access to the shared folder. It was possible to read files but I was not allowed to write files to the shared source path folder.



          Unix & Linux - KVM / QEMU / Virt-Manager : How can I store files in the mounted shared folder



          The root cause is that the guest system is running as libvirt-qemu user. What you should do to create files from within the running guest system in the mounted shared folder are these steps :



          In Virt-Manager -> Add Hardware -> Filesystem select Mapped as Mode setting for the VM.



          Change permissions for the shared folders : sudo chmod -R 777 /<path-to-shared-folder>



          Change the owner to your username : sudo chown -R user:user /<path-to-shared folder>



          Change the permissions for virtual disk files : sudo chmod -R 777 /<path-to-virtual-disks>



          Change the owner to your username : sudo chown -R user:user /<path-to-virtual-disks>



          Add your username to the libvirtd group : sudo usermod -G libvirtd -a <your-user-name>



          Give full permissions to the libvirt-qemu user : sudo setfacl -R -m u:libvirt-qemu:rwx /*



          Note : * = Specify the folder directory hierarchy you want to give libvirt-qemu the permissions.



          Reboot the host operating systems ... now you should be able to create files in the guest system.



          Information about 9p virtio -> Sharing Host files with the Guest | QEMU Documentation 9psetup



          Mode specifies the security mode for accessing the source. Mapped specifies that the source is accessed with the permission settings of the hypervisor. Passthrough specifies that the source is accessed with the user's permission settings that are set from inside the virtual guest machine. This is the default mode. Squash is similar to Passthrough, the difference is that the failure of privileged operations like chown are ignored, this makes a Passthrough mode usable for users who are running the hypervisor without elevated privileges.






          share|improve this answer


























          • That shows a workaround, but doesn't explain the meaning of Mapping and friends.

            – anatoly techtonik
            May 15 '16 at 16:17











          • That makes it more clear, thanks. I don't understand how passthrough could work, because I don't have this vagrant:vagrant user on host. What if I run root user inside guess - will it be able to access everything on host in passthrough mode just because name matches?

            – anatoly techtonik
            May 15 '16 at 17:54











          • @anatolytechtonik : You can try it out ... but I assume that you want to run it as normal user, which is the safer way and the reason why I suggested the solution that worked without further problems in my case. :)

            – cl-netbox
            May 15 '16 at 17:58













          • Before trying I'd like to understand how it should work.

            – anatoly techtonik
            May 16 '16 at 5:16











          • @anatolytechtonik : The most relevant part is about giving the necessary permissions and the difference between the modes are explained. :)

            – cl-netbox
            May 16 '16 at 8:07



















          0














          Share modes define how the virtualised (p9fs) file system is presented to the guest machine. There are important implications for permission mapping. To understand this, it's important to remember that the virtualised file system needs to manage permissions of files and they may not be the same in the host as they are in the guest.



          The best docs I have found regarding the modes is from the libvirt docs:



          The filesystem block has an optional attribute accessmode which specifies the security mode for accessing the source (since 0.8.5). Currently this only works with type='mount' for the QEMU/KVM driver. The possible values are:





          • passthrough
            The source is accessed with the permissions of the user inside the guest. This is the default accessmode if one is not specified. More info. Beware that changes to permissions/ownership will affect all guests using that filesystem. This mode is generally quite fast.


          • mapped
            The source is accessed with the permissions of the hypervisor (QEMU process). More info.
            This means you need to make sure that files on the hypervisor are accessible to the QEMU process (username libvirt-qemu on my setup). The advantage is that file attributes and permissions are "mapped" for the guest so that they are independent changes elsewhere (as long as the files stay accessible). If your host system supports ACLs, this mode will also allow proper ACL support in the guest. This mode is generally a bit slower than passthrough.


          • squash
            Similar to 'passthrough', the exception is that failure of privileged operations like 'chown' are ignored. This makes a passthrough-like mode usable for people who run the hypervisor as non-root. More info






          share|improve this answer








          New contributor




          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.





















          • also note that passthrough mode does seem to have some issues with writing files, I have also encountered the issue listed here: serverfault.com/questions/559726/… Squash mode seems to work better

            – FGiorlando
            2 days ago













          Your Answer








          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "89"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: true,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: 10,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faskubuntu.com%2fquestions%2f772784%2f9p-libvirt-qemu-share-modes%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          2














          I once had a very similar problem, providing read-write access to the shared folder. It was possible to read files but I was not allowed to write files to the shared source path folder.



          Unix & Linux - KVM / QEMU / Virt-Manager : How can I store files in the mounted shared folder



          The root cause is that the guest system is running as libvirt-qemu user. What you should do to create files from within the running guest system in the mounted shared folder are these steps :



          In Virt-Manager -> Add Hardware -> Filesystem select Mapped as Mode setting for the VM.



          Change permissions for the shared folders : sudo chmod -R 777 /<path-to-shared-folder>



          Change the owner to your username : sudo chown -R user:user /<path-to-shared folder>



          Change the permissions for virtual disk files : sudo chmod -R 777 /<path-to-virtual-disks>



          Change the owner to your username : sudo chown -R user:user /<path-to-virtual-disks>



          Add your username to the libvirtd group : sudo usermod -G libvirtd -a <your-user-name>



          Give full permissions to the libvirt-qemu user : sudo setfacl -R -m u:libvirt-qemu:rwx /*



          Note : * = Specify the folder directory hierarchy you want to give libvirt-qemu the permissions.



          Reboot the host operating systems ... now you should be able to create files in the guest system.



          Information about 9p virtio -> Sharing Host files with the Guest | QEMU Documentation 9psetup



          Mode specifies the security mode for accessing the source. Mapped specifies that the source is accessed with the permission settings of the hypervisor. Passthrough specifies that the source is accessed with the user's permission settings that are set from inside the virtual guest machine. This is the default mode. Squash is similar to Passthrough, the difference is that the failure of privileged operations like chown are ignored, this makes a Passthrough mode usable for users who are running the hypervisor without elevated privileges.






          share|improve this answer


























          • That shows a workaround, but doesn't explain the meaning of Mapping and friends.

            – anatoly techtonik
            May 15 '16 at 16:17











          • That makes it more clear, thanks. I don't understand how passthrough could work, because I don't have this vagrant:vagrant user on host. What if I run root user inside guess - will it be able to access everything on host in passthrough mode just because name matches?

            – anatoly techtonik
            May 15 '16 at 17:54











          • @anatolytechtonik : You can try it out ... but I assume that you want to run it as normal user, which is the safer way and the reason why I suggested the solution that worked without further problems in my case. :)

            – cl-netbox
            May 15 '16 at 17:58













          • Before trying I'd like to understand how it should work.

            – anatoly techtonik
            May 16 '16 at 5:16











          • @anatolytechtonik : The most relevant part is about giving the necessary permissions and the difference between the modes are explained. :)

            – cl-netbox
            May 16 '16 at 8:07
















          2














          I once had a very similar problem, providing read-write access to the shared folder. It was possible to read files but I was not allowed to write files to the shared source path folder.



          Unix & Linux - KVM / QEMU / Virt-Manager : How can I store files in the mounted shared folder



          The root cause is that the guest system is running as libvirt-qemu user. What you should do to create files from within the running guest system in the mounted shared folder are these steps :



          In Virt-Manager -> Add Hardware -> Filesystem select Mapped as Mode setting for the VM.



          Change permissions for the shared folders : sudo chmod -R 777 /<path-to-shared-folder>



          Change the owner to your username : sudo chown -R user:user /<path-to-shared folder>



          Change the permissions for virtual disk files : sudo chmod -R 777 /<path-to-virtual-disks>



          Change the owner to your username : sudo chown -R user:user /<path-to-virtual-disks>



          Add your username to the libvirtd group : sudo usermod -G libvirtd -a <your-user-name>



          Give full permissions to the libvirt-qemu user : sudo setfacl -R -m u:libvirt-qemu:rwx /*



          Note : * = Specify the folder directory hierarchy you want to give libvirt-qemu the permissions.



          Reboot the host operating systems ... now you should be able to create files in the guest system.



          Information about 9p virtio -> Sharing Host files with the Guest | QEMU Documentation 9psetup



          Mode specifies the security mode for accessing the source. Mapped specifies that the source is accessed with the permission settings of the hypervisor. Passthrough specifies that the source is accessed with the user's permission settings that are set from inside the virtual guest machine. This is the default mode. Squash is similar to Passthrough, the difference is that the failure of privileged operations like chown are ignored, this makes a Passthrough mode usable for users who are running the hypervisor without elevated privileges.






          share|improve this answer


























          • That shows a workaround, but doesn't explain the meaning of Mapping and friends.

            – anatoly techtonik
            May 15 '16 at 16:17











          • That makes it more clear, thanks. I don't understand how passthrough could work, because I don't have this vagrant:vagrant user on host. What if I run root user inside guess - will it be able to access everything on host in passthrough mode just because name matches?

            – anatoly techtonik
            May 15 '16 at 17:54











          • @anatolytechtonik : You can try it out ... but I assume that you want to run it as normal user, which is the safer way and the reason why I suggested the solution that worked without further problems in my case. :)

            – cl-netbox
            May 15 '16 at 17:58













          • Before trying I'd like to understand how it should work.

            – anatoly techtonik
            May 16 '16 at 5:16











          • @anatolytechtonik : The most relevant part is about giving the necessary permissions and the difference between the modes are explained. :)

            – cl-netbox
            May 16 '16 at 8:07














          2












          2








          2







          I once had a very similar problem, providing read-write access to the shared folder. It was possible to read files but I was not allowed to write files to the shared source path folder.



          Unix & Linux - KVM / QEMU / Virt-Manager : How can I store files in the mounted shared folder



          The root cause is that the guest system is running as libvirt-qemu user. What you should do to create files from within the running guest system in the mounted shared folder are these steps :



          In Virt-Manager -> Add Hardware -> Filesystem select Mapped as Mode setting for the VM.



          Change permissions for the shared folders : sudo chmod -R 777 /<path-to-shared-folder>



          Change the owner to your username : sudo chown -R user:user /<path-to-shared folder>



          Change the permissions for virtual disk files : sudo chmod -R 777 /<path-to-virtual-disks>



          Change the owner to your username : sudo chown -R user:user /<path-to-virtual-disks>



          Add your username to the libvirtd group : sudo usermod -G libvirtd -a <your-user-name>



          Give full permissions to the libvirt-qemu user : sudo setfacl -R -m u:libvirt-qemu:rwx /*



          Note : * = Specify the folder directory hierarchy you want to give libvirt-qemu the permissions.



          Reboot the host operating systems ... now you should be able to create files in the guest system.



          Information about 9p virtio -> Sharing Host files with the Guest | QEMU Documentation 9psetup



          Mode specifies the security mode for accessing the source. Mapped specifies that the source is accessed with the permission settings of the hypervisor. Passthrough specifies that the source is accessed with the user's permission settings that are set from inside the virtual guest machine. This is the default mode. Squash is similar to Passthrough, the difference is that the failure of privileged operations like chown are ignored, this makes a Passthrough mode usable for users who are running the hypervisor without elevated privileges.






          share|improve this answer















          I once had a very similar problem, providing read-write access to the shared folder. It was possible to read files but I was not allowed to write files to the shared source path folder.



          Unix & Linux - KVM / QEMU / Virt-Manager : How can I store files in the mounted shared folder



          The root cause is that the guest system is running as libvirt-qemu user. What you should do to create files from within the running guest system in the mounted shared folder are these steps :



          In Virt-Manager -> Add Hardware -> Filesystem select Mapped as Mode setting for the VM.



          Change permissions for the shared folders : sudo chmod -R 777 /<path-to-shared-folder>



          Change the owner to your username : sudo chown -R user:user /<path-to-shared folder>



          Change the permissions for virtual disk files : sudo chmod -R 777 /<path-to-virtual-disks>



          Change the owner to your username : sudo chown -R user:user /<path-to-virtual-disks>



          Add your username to the libvirtd group : sudo usermod -G libvirtd -a <your-user-name>



          Give full permissions to the libvirt-qemu user : sudo setfacl -R -m u:libvirt-qemu:rwx /*



          Note : * = Specify the folder directory hierarchy you want to give libvirt-qemu the permissions.



          Reboot the host operating systems ... now you should be able to create files in the guest system.



          Information about 9p virtio -> Sharing Host files with the Guest | QEMU Documentation 9psetup



          Mode specifies the security mode for accessing the source. Mapped specifies that the source is accessed with the permission settings of the hypervisor. Passthrough specifies that the source is accessed with the user's permission settings that are set from inside the virtual guest machine. This is the default mode. Squash is similar to Passthrough, the difference is that the failure of privileged operations like chown are ignored, this makes a Passthrough mode usable for users who are running the hypervisor without elevated privileges.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Apr 13 '17 at 12:37









          Community

          1




          1










          answered May 15 '16 at 15:50









          cl-netboxcl-netbox

          25.8k572113




          25.8k572113













          • That shows a workaround, but doesn't explain the meaning of Mapping and friends.

            – anatoly techtonik
            May 15 '16 at 16:17











          • That makes it more clear, thanks. I don't understand how passthrough could work, because I don't have this vagrant:vagrant user on host. What if I run root user inside guess - will it be able to access everything on host in passthrough mode just because name matches?

            – anatoly techtonik
            May 15 '16 at 17:54











          • @anatolytechtonik : You can try it out ... but I assume that you want to run it as normal user, which is the safer way and the reason why I suggested the solution that worked without further problems in my case. :)

            – cl-netbox
            May 15 '16 at 17:58













          • Before trying I'd like to understand how it should work.

            – anatoly techtonik
            May 16 '16 at 5:16











          • @anatolytechtonik : The most relevant part is about giving the necessary permissions and the difference between the modes are explained. :)

            – cl-netbox
            May 16 '16 at 8:07



















          • That shows a workaround, but doesn't explain the meaning of Mapping and friends.

            – anatoly techtonik
            May 15 '16 at 16:17











          • That makes it more clear, thanks. I don't understand how passthrough could work, because I don't have this vagrant:vagrant user on host. What if I run root user inside guess - will it be able to access everything on host in passthrough mode just because name matches?

            – anatoly techtonik
            May 15 '16 at 17:54











          • @anatolytechtonik : You can try it out ... but I assume that you want to run it as normal user, which is the safer way and the reason why I suggested the solution that worked without further problems in my case. :)

            – cl-netbox
            May 15 '16 at 17:58













          • Before trying I'd like to understand how it should work.

            – anatoly techtonik
            May 16 '16 at 5:16











          • @anatolytechtonik : The most relevant part is about giving the necessary permissions and the difference between the modes are explained. :)

            – cl-netbox
            May 16 '16 at 8:07

















          That shows a workaround, but doesn't explain the meaning of Mapping and friends.

          – anatoly techtonik
          May 15 '16 at 16:17





          That shows a workaround, but doesn't explain the meaning of Mapping and friends.

          – anatoly techtonik
          May 15 '16 at 16:17













          That makes it more clear, thanks. I don't understand how passthrough could work, because I don't have this vagrant:vagrant user on host. What if I run root user inside guess - will it be able to access everything on host in passthrough mode just because name matches?

          – anatoly techtonik
          May 15 '16 at 17:54





          That makes it more clear, thanks. I don't understand how passthrough could work, because I don't have this vagrant:vagrant user on host. What if I run root user inside guess - will it be able to access everything on host in passthrough mode just because name matches?

          – anatoly techtonik
          May 15 '16 at 17:54













          @anatolytechtonik : You can try it out ... but I assume that you want to run it as normal user, which is the safer way and the reason why I suggested the solution that worked without further problems in my case. :)

          – cl-netbox
          May 15 '16 at 17:58







          @anatolytechtonik : You can try it out ... but I assume that you want to run it as normal user, which is the safer way and the reason why I suggested the solution that worked without further problems in my case. :)

          – cl-netbox
          May 15 '16 at 17:58















          Before trying I'd like to understand how it should work.

          – anatoly techtonik
          May 16 '16 at 5:16





          Before trying I'd like to understand how it should work.

          – anatoly techtonik
          May 16 '16 at 5:16













          @anatolytechtonik : The most relevant part is about giving the necessary permissions and the difference between the modes are explained. :)

          – cl-netbox
          May 16 '16 at 8:07





          @anatolytechtonik : The most relevant part is about giving the necessary permissions and the difference between the modes are explained. :)

          – cl-netbox
          May 16 '16 at 8:07













          0














          Share modes define how the virtualised (p9fs) file system is presented to the guest machine. There are important implications for permission mapping. To understand this, it's important to remember that the virtualised file system needs to manage permissions of files and they may not be the same in the host as they are in the guest.



          The best docs I have found regarding the modes is from the libvirt docs:



          The filesystem block has an optional attribute accessmode which specifies the security mode for accessing the source (since 0.8.5). Currently this only works with type='mount' for the QEMU/KVM driver. The possible values are:





          • passthrough
            The source is accessed with the permissions of the user inside the guest. This is the default accessmode if one is not specified. More info. Beware that changes to permissions/ownership will affect all guests using that filesystem. This mode is generally quite fast.


          • mapped
            The source is accessed with the permissions of the hypervisor (QEMU process). More info.
            This means you need to make sure that files on the hypervisor are accessible to the QEMU process (username libvirt-qemu on my setup). The advantage is that file attributes and permissions are "mapped" for the guest so that they are independent changes elsewhere (as long as the files stay accessible). If your host system supports ACLs, this mode will also allow proper ACL support in the guest. This mode is generally a bit slower than passthrough.


          • squash
            Similar to 'passthrough', the exception is that failure of privileged operations like 'chown' are ignored. This makes a passthrough-like mode usable for people who run the hypervisor as non-root. More info






          share|improve this answer








          New contributor




          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.





















          • also note that passthrough mode does seem to have some issues with writing files, I have also encountered the issue listed here: serverfault.com/questions/559726/… Squash mode seems to work better

            – FGiorlando
            2 days ago


















          0














          Share modes define how the virtualised (p9fs) file system is presented to the guest machine. There are important implications for permission mapping. To understand this, it's important to remember that the virtualised file system needs to manage permissions of files and they may not be the same in the host as they are in the guest.



          The best docs I have found regarding the modes is from the libvirt docs:



          The filesystem block has an optional attribute accessmode which specifies the security mode for accessing the source (since 0.8.5). Currently this only works with type='mount' for the QEMU/KVM driver. The possible values are:





          • passthrough
            The source is accessed with the permissions of the user inside the guest. This is the default accessmode if one is not specified. More info. Beware that changes to permissions/ownership will affect all guests using that filesystem. This mode is generally quite fast.


          • mapped
            The source is accessed with the permissions of the hypervisor (QEMU process). More info.
            This means you need to make sure that files on the hypervisor are accessible to the QEMU process (username libvirt-qemu on my setup). The advantage is that file attributes and permissions are "mapped" for the guest so that they are independent changes elsewhere (as long as the files stay accessible). If your host system supports ACLs, this mode will also allow proper ACL support in the guest. This mode is generally a bit slower than passthrough.


          • squash
            Similar to 'passthrough', the exception is that failure of privileged operations like 'chown' are ignored. This makes a passthrough-like mode usable for people who run the hypervisor as non-root. More info






          share|improve this answer








          New contributor




          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.





















          • also note that passthrough mode does seem to have some issues with writing files, I have also encountered the issue listed here: serverfault.com/questions/559726/… Squash mode seems to work better

            – FGiorlando
            2 days ago
















          0












          0








          0







          Share modes define how the virtualised (p9fs) file system is presented to the guest machine. There are important implications for permission mapping. To understand this, it's important to remember that the virtualised file system needs to manage permissions of files and they may not be the same in the host as they are in the guest.



          The best docs I have found regarding the modes is from the libvirt docs:



          The filesystem block has an optional attribute accessmode which specifies the security mode for accessing the source (since 0.8.5). Currently this only works with type='mount' for the QEMU/KVM driver. The possible values are:





          • passthrough
            The source is accessed with the permissions of the user inside the guest. This is the default accessmode if one is not specified. More info. Beware that changes to permissions/ownership will affect all guests using that filesystem. This mode is generally quite fast.


          • mapped
            The source is accessed with the permissions of the hypervisor (QEMU process). More info.
            This means you need to make sure that files on the hypervisor are accessible to the QEMU process (username libvirt-qemu on my setup). The advantage is that file attributes and permissions are "mapped" for the guest so that they are independent changes elsewhere (as long as the files stay accessible). If your host system supports ACLs, this mode will also allow proper ACL support in the guest. This mode is generally a bit slower than passthrough.


          • squash
            Similar to 'passthrough', the exception is that failure of privileged operations like 'chown' are ignored. This makes a passthrough-like mode usable for people who run the hypervisor as non-root. More info






          share|improve this answer








          New contributor




          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.










          Share modes define how the virtualised (p9fs) file system is presented to the guest machine. There are important implications for permission mapping. To understand this, it's important to remember that the virtualised file system needs to manage permissions of files and they may not be the same in the host as they are in the guest.



          The best docs I have found regarding the modes is from the libvirt docs:



          The filesystem block has an optional attribute accessmode which specifies the security mode for accessing the source (since 0.8.5). Currently this only works with type='mount' for the QEMU/KVM driver. The possible values are:





          • passthrough
            The source is accessed with the permissions of the user inside the guest. This is the default accessmode if one is not specified. More info. Beware that changes to permissions/ownership will affect all guests using that filesystem. This mode is generally quite fast.


          • mapped
            The source is accessed with the permissions of the hypervisor (QEMU process). More info.
            This means you need to make sure that files on the hypervisor are accessible to the QEMU process (username libvirt-qemu on my setup). The advantage is that file attributes and permissions are "mapped" for the guest so that they are independent changes elsewhere (as long as the files stay accessible). If your host system supports ACLs, this mode will also allow proper ACL support in the guest. This mode is generally a bit slower than passthrough.


          • squash
            Similar to 'passthrough', the exception is that failure of privileged operations like 'chown' are ignored. This makes a passthrough-like mode usable for people who run the hypervisor as non-root. More info







          share|improve this answer








          New contributor




          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          share|improve this answer



          share|improve this answer






          New contributor




          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.









          answered Jan 10 at 15:44









          FGiorlandoFGiorlando

          101




          101




          New contributor




          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.





          New contributor





          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.






          FGiorlando is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.













          • also note that passthrough mode does seem to have some issues with writing files, I have also encountered the issue listed here: serverfault.com/questions/559726/… Squash mode seems to work better

            – FGiorlando
            2 days ago





















          • also note that passthrough mode does seem to have some issues with writing files, I have also encountered the issue listed here: serverfault.com/questions/559726/… Squash mode seems to work better

            – FGiorlando
            2 days ago



















          also note that passthrough mode does seem to have some issues with writing files, I have also encountered the issue listed here: serverfault.com/questions/559726/… Squash mode seems to work better

          – FGiorlando
          2 days ago







          also note that passthrough mode does seem to have some issues with writing files, I have also encountered the issue listed here: serverfault.com/questions/559726/… Squash mode seems to work better

          – FGiorlando
          2 days ago




















          draft saved

          draft discarded




















































          Thanks for contributing an answer to Ask Ubuntu!


          • Please be sure to answer the question. Provide details and share your research!

          But avoid



          • Asking for help, clarification, or responding to other answers.

          • Making statements based on opinion; back them up with references or personal experience.


          To learn more, see our tips on writing great answers.




          draft saved


          draft discarded














          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faskubuntu.com%2fquestions%2f772784%2f9p-libvirt-qemu-share-modes%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown





















































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown

































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown







          Popular posts from this blog

          數位音樂下載

          When can things happen in Etherscan, such as the picture below?

          格利澤436b