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246 lines
8.7 KiB
Markdown
246 lines
8.7 KiB
Markdown
---
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lang: en
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layout: doc
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permalink: /doc/software-update-dom0/
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redirect_from:
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- /en/doc/software-update-dom0/
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- /doc/SoftwareUpdateDom0/
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- /wiki/SoftwareUpdateDom0/
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ref: 194
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title: Installing and updating software in dom0
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---
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# Installing and updating software in dom0
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Updating [dom0] is one of the main steps in [Updating Qubes OS].
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It is very important to keep dom0 up-to-date with the latest [security] updates.
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We also publish dom0 updates for various non-security bug fixes and enhancements to Qubes components.
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In addition, you may wish to update the kernel, drivers, or libraries in dom0 when [troubleshooting newer hardware].
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## Security
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Since there is no networking in dom0, any bugs discovered in dom0 desktop components (e.g., the window manager) are unlikely to pose a problem for Qubes, since none of the third-party software running in dom0 is accessible from VMs or the network in any way.
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Nonetheless, since software running in dom0 can potentially exercise full control over the system, it is important to install only trusted software in dom0.
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The install/update process is split into two phases: *resolve and download* and *verify and install*.
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The *resolve and download* phase is handled by the UpdateVM.
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(The role of UpdateVM can be assigned to any VM in the Qube Manager, and there are no significant security implications in this choice.
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By default, this role is assigned to the FirewallVM.)
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After the UpdateVM has successfully downloaded new packages, they are sent to dom0, where they are verified and installed.
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This separation of duties significantly reduces the attack surface, since all of the network and metadata processing code is removed from the TCB.
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Although this update scheme is far more secure than directly downloading updates in dom0, it is not invulnerable.
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For example, there is nothing that the Qubes OS Project can feasibly do to prevent a malicious RPM from exploiting a hypothetical bug in the cryptographic signature verification operation.
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At best, we could switch to a different distro or package manager, but any of them could be vulnerable to the same (or a similar) attack.
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While we could, in theory, write a custom solution, it would only be effective if Qubes repos included all of the regular TemplateVM distro's updates, and this would be far too costly for us to maintain.
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## How to update dom0
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In the Qube Manager, simply select dom0 in the VM list, then click the **Update VM system** button (the blue, downward-pointing arrow).
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In addition, updating dom0 has been made more convenient: You will be prompted on the desktop whenever new dom0 updates are available and given the choice to run the update with a single click.
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Alternatively, command-line tools are available for accomplishing various update-related tasks (some of which are not available via Qubes VM Manager).
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In order to update dom0 from the command line, start a console in dom0 and then run one of the following commands:
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To check and install updates for dom0 software:
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```
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$ sudo qubes-dom0-update
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```
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## How to install a specific package
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To install additional packages in dom0 (usually not recommended):
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```
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$ sudo qubes-dom0-update anti-evil-maid
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```
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You may also pass the `--enablerepo=` option in order to enable optional repositories (see yum configuration in dom0).
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However, this is only for advanced users who really understand what they are doing.
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You can also pass commands to `dnf` using `--action=...`.
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## How to downgrade a specific package
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**WARNING:** Downgrading a package can expose your system to security vulnerabilities.
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1. Download an older version of the package:
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~~~
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sudo qubes-dom0-update package-version
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~~~
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Dnf will say that there is no update, but the package will nonetheless be downloaded to dom0.
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2. Downgrade the package:
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~~~
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sudo dnf downgrade package-version
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~~~
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## How to re-install a package
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You can re-install in a similar fashion to downgrading.
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1. Download the package:
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~~~
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sudo qubes-dom0-update package
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~~~
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Dnf will say that there is no update, but the package will nonetheless be downloaded to dom0.
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2. Re-install the package:
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~~~
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sudo dnf reinstall package
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~~~
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Note that `dnf` will only re-install if the installed and downloaded versions match.
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You can ensure they match by either updating the package to the latest version, or specifying the package version in the first step using the form `package-version`.
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## How to uninstall a package
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If you've installed a package such as anti-evil-maid, you can remove it with the following command:
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```
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sudo dnf remove anti-evil-maid
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```
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## Testing repositories
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There are three Qubes dom0 [testing] repositories:
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- `qubes-dom0-current-testing` -- testing packages that will eventually land in the stable
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(`current`) repository
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- `qubes-dom0-security-testing` -- a subset of `qubes-dom0-current-testing` that contains packages
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that qualify as security fixes
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- `qubes-dom0-unstable` -- packages that are not intended to land in the stable (`qubes-dom0-current`)
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repository; mostly experimental debugging packages
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To temporarily enable any of these repos, use the `--enablerepo=<repo-name>` option.
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Example commands:
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~~~
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sudo qubes-dom0-update --enablerepo=qubes-dom0-current-testing
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sudo qubes-dom0-update --enablerepo=qubes-dom0-security-testing
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sudo qubes-dom0-update --enablerepo=qubes-dom0-unstable
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~~~
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To enable or disable any of these repos permanently, change the corresponding `enabled` value to `1` in
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`/etc/yum.repos.d/qubes-dom0.repo`.
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## Contributed package repository
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Please see [installing contributed packages].
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## Kernel upgrade
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This section describes upgrading the kernel in dom0 and domUs.
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### dom0
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The packages `kernel` and `kernel-latest` are for dom0.
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In the `current` repository:
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- `kernel`: an older LTS kernel that has passed Qubes [testing] (the default dom0 kernel)
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- `kernel-latest`: the latest release from kernel.org that has passed Qubes [testing] (useful for [troubleshooting newer hardware])
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In the `current-testing` repository:
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- `kernel`: the latest LTS kernel from kernel.org at the time it was built.
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- `kernel-latest`: the latest release from kernel.org at the time it was built.
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### domU
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The packages `kernel-qubes-vm` and `kernel-latest-qubes-vm` are for domUs.
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See [Managing VM kernel] for more information.
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### Example
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(Note that the following example enables the unstable repo.)
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~~~
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sudo qubes-dom0-update --enablerepo=qubes-dom0-unstable kernel kernel-qubes-vm
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~~~
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If the update process does not automatically do it (you should see it mentioned in the CLI output
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from the update command), you may need to manually rebuild the EFI or grub config depending on which
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your system uses.
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*EFI*: Replace the example version numbers with the one you are upgrading to.
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~~~
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sudo dracut -f /boot/efi/EFI/qubes/initramfs-4.14.35-1.pvops.qubes.x86_64.img 4.14.35-1.pvops.qubes.x86_64
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~~~
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*Grub2*
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~~~
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sudo grub2-mkconfig -o /boot/grub2/grub.cfg
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~~~
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Reboot required.
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If you wish to upgrade to a kernel that is not available from the repos, then
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there is no easy way to do so, but [it may still be possible if you're willing
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to do a lot of work yourself](https://groups.google.com/d/msg/qubes-users/m8sWoyV58_E/HYdReRIYBAAJ).
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## Changing default kernel
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This section describes changing the default kernel in dom0.
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It is sometimes needed if you have upgraded to a newer kernel and are having problems booting, for example.
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The procedure varies depending on if you are booting with UEFI or grub.
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On the next kernel update, the default will revert to the newest.
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*EFI*
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~~~
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sudo nano /boot/efi/EFI/qubes/xen.cfg
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~~~
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In the `[global]` section at the top, change the `default=` line to match one of the three boot entries listed below.
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For example,
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~~~
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default=4.19.67-1.pvops.qubes.x86_64
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~~~
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*Grub2*
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~~~
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sudo nano /etc/default/grub
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[update the following two lines, add if needed]
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GRUB_DISABLE_SUBMENU=false
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GRUB_SAVEDEFAULT=true
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[save and exit nano]
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sudo grub2-mkconfig -o /boot/grub2/grub.cfg
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~~~
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Then, reboot.
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Once the grub menu appears, choose "Advanced Options for Qubes (with Xen hypervisor)".
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Next, the top menu item (for example, "Xen hypervisor, version 4.8.5-9.fc25").
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Select the kernel you want as default, and it will be remembered for next boot.
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## Updating over Tor
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Requires installed [Whonix](/doc/privacy/whonix/).
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Go to Qubes VM Manager -> System -> Global Settings.
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See the UpdateVM setting.
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Choose your desired Whonix-Gateway ProxyVM from the list.
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For example: sys-whonix.
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`
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Qubes VM Manager -> System -> Global Settings -> UpdateVM -> sys-whonix
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`
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[dom0]: /doc/glossary/#dom0
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[Updating Qubes OS]: /doc/updating-qubes-os/
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[security]: /security/
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[testing]: /doc/testing/
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[troubleshooting newer hardware]: /doc/newer-hardware-troubleshooting/
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[Managing VM kernel]: /doc/managing-vm-kernel/
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[installing contributed packages]: /doc/installing-contributed-packages/
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