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+# FAQ
+
+[TOC]
+
+### What operating systems are supported? {#supported-os}
+
+Today, gVisor requires Linux.
+
+### What CPU architectures are supported? {#supported-cpus}
+
+gVisor currently supports [x86_64/AMD64](https://en.wikipedia.org/wiki/X86-64)
+compatible processors. Preliminary support is also available for
+[ARM64](https://en.wikipedia.org/wiki/ARM_architecture#AArch64).
+
+### Do I need to modify my Linux application to use gVisor? {#modify-app}
+
+No. gVisor is capable of running unmodified Linux binaries.
+
+### What binary formats does gVisor support? {#supported-binaries}
+
+gVisor supports Linux
+[ELF](https://en.wikipedia.org/wiki/Executable_and_Linkable_Format) binaries.
+
+Binaries run in gVisor should be built for the
+[AMD64](https://en.wikipedia.org/wiki/X86-64) or
+[AArch64](https://en.wikipedia.org/wiki/ARM_architecture#AArch64) CPU
+architectures.
+
+### Can I run Docker images using gVisor? {#docker-images}
+
+Yes. Please see the [Docker Quick Start][docker].
+
+### Can I run Kubernetes pods using gVisor? {#k8s-pods}
+
+Yes. Please see the [Kubernetes Quick Start][k8s].
+
+### What's the security model? {#security-model}
+
+See the [Security Model][security-model].
+
+## Troubleshooting
+
+### My container runs fine with `runc` but fails with `runsc` {#app-compatibility}
+
+If you’re having problems running a container with `runsc` it’s most likely due
+to a compatibility issue or a missing feature in gVisor. See
+[Debugging][debugging].
+
+### When I run my container, docker fails with: `open /run/containerd/.../<containerid>/log.json: no such file or directory` {#memfd-create}
+
+You are using an older version of Linux which doesn't support `memfd_create`.
+
+This is tracked in [bug #268](https://gvisor.dev/issue/268).
+
+### When I run my container, docker fails with: `flag provided but not defined: -console` {#old-docker}
+
+You're using an old version of Docker. See [Docker Quick Start][docker].
+
+### I can’t see a file copied with: `docker cp` {#fs-cache}
+
+For performance reasons, gVisor caches directory contents, and therefore it may
+not realize a new file was copied to a given directory. To invalidate the cache
+and force a refresh, create a file under the directory in question and list the
+contents again.
+
+As a workaround, shared root filesystem can be enabled. See
+[Filesystem][filesystem].
+
+This bug is tracked in [bug #4](https://gvisor.dev/issue/4).
+
+Note that `kubectl cp` works because it does the copy by exec'ing inside the
+sandbox, and thus gVisor's internal cache is made aware of the new files and
+directories.
+
+### I'm getting an error like: `panic: unable to attach: operation not permitted` or `fork/exec /proc/self/exe: invalid argument: unknown` {#runsc-perms}
+
+Make sure that permissions and the owner is correct on the `runsc` binary.
+
+```bash
+sudo chown root:root /usr/local/bin/runsc
+sudo chmod 0755 /usr/local/bin/runsc
+```
+
+### I'm getting an error like `mount submount "/etc/hostname": creating mount with source ".../hostname": input/output error: unknown.` {#memlock}
+
+There is a bug in Linux kernel versions 5.1 to 5.3.15, 5.4.2, and 5.5. Upgrade
+to a newer kernel or add the following to
+`/lib/systemd/system/containerd.service` as a workaround.
+
+```
+LimitMEMLOCK=infinity
+```
+
+And run `systemctl daemon-reload && systemctl restart containerd` to restart
+containerd.
+
+See [issue #1765](https://gvisor.dev/issue/1765) for more details.
+
+### My container cannot resolve another container's name when using Docker user defined bridge {#docker-bridge}
+
+This is normally indicated by errors like `bad address 'container-name'` when
+trying to communicate to another container in the same network.
+
+Docker user defined bridge uses an embedded DNS server bound to the loopback
+interface on address 127.0.0.10. This requires access to the host network in
+order to communicate to the DNS server. runsc network is isolated from the host
+and cannot access the DNS server on the host network without breaking the
+sandbox isolation. There are a few different workarounds you can try:
+
+* Use default bridge network with `--link` to connect containers. Default
+ bridge doesn't use embedded DNS.
+* Use [`--network=host`][host-net] option in runsc, however beware that it
+ will use the host network stack and is less secure.
+* Use IPs instead of container names.
+* Use [Kubernetes][k8s]. Container name lookup works fine in Kubernetes.
+
+[security-model]: /docs/architecture_guide/security/
+[host-net]: /docs/user_guide/networking/#network-passthrough
+[debugging]: /docs/user_guide/debugging/
+[filesystem]: /docs/user_guide/filesystem/
+[docker]: /docs/user_guide/quick_start/docker/
+[k8s]: /docs/user_guide/quick_start/kubernetes/