安全计算模式（secure computing mode，seccomp）是 Linux 内核功能。可以使用它来限制容器内可用的操作。seccomp() 系统调用在调用进程的 seccomp 状态下运行。可以使用此功能来限制你的应用程序的访问权限。
只有在使用 seccomp 构建 Docker 并且内核配置了 CONFIG_SECCOMP 的情况下，此功能才可用。要检查你的内核是否支持 seccomp：
$ cat /boot/config-`uname -r` | grep CONFIG_SECCOMP=
CONFIG_SECCOMP=y- 1
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注意：
seccomp配置文件需要 seccomp 2.2.1，这在 Ubuntu 14.04，Debian Wheezy 或 Debian Jessie 中不可用。要在这些发行版上使用seccomp，必须下载 最新的静态 Linux 二进制文件（而不是软件包）。
1. 为容器传递配置文件
默认的 seccomp 配置文件为使用 seccomp 运行容器提供了一个合理的设置，并禁用了大约 44 个超过 300+ 的系统调用。它具有适度的保护性，同时提供广泛的应用兼容性。默认的 Docker 配置文件可以在 这里 找到。
实际上，该配置文件是白名单，默认情况下阻止访问所有的系统调用，然后将特定的系统调用列入白名单。该配置文件工作时需要定义 SCMP_ACT_ERRNO 的 defaultAction 并仅针对特定的系统调用覆盖该 action。SCMP_ACT_ERRNO 的影响是触发 Permission Denied 错误。接下来，配置文件中通过将 action 被覆盖为 SCMP_ACT_ALLOW，定义一个完全允许的系统调用的特定列表。最后，一些特定规则适用于个别的系统调用，如 personality，socket，socketcall 等，以允许具有特定参数的那些系统调用的变体（to allow variants of those system calls with specific arguments）。
seccomp 有助于以最小权限运行 Docker 容器。不建议更改默认的 seccomp 配置文件。
运行容器时，如果没有通过 --security-opt 选项覆盖容器，则会使用默认配置。例如，以下显式指定了一个策略：
$ docker run --rm \
-it \
--security-opt seccomp=/path/to/seccomp/profile.json \
hello-world- 1
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1.1 默认配置文件阻止的重要的系统调用
Docker 的默认 seccomp 配置文件是一个白名单，它指定了允许的调用。下表列出了由于不在白名单而被有效阻止的重要（但不是全部）系统调用。该表包含每个系统调用被阻止的原因。
| Syscall | Description |
|---|---|
| acct | Accounting syscall which could let containers disable their own resource limits or process accounting. Also gated by CAP_SYS_PACCT. |
| add_key | Prevent containers from using the kernel keyring, which is not namespaced. |
| adjtimex | Similar to clock_settime and settimeofday, time/date is not namespaced. Also gated by CAP_SYS_TIME. |
| bpf | Deny loading potentially persistent bpf programs into kernel, already gated by CAP_SYS_ADMIN. |
| clock_adjtime | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
| clock_settime | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
| clone | Deny cloning new namespaces. Also gated by CAP_SYS_ADMIN for CLONE_* flags, except CLONE_USERNS. |
| create_module | Deny manipulation and functions on kernel modules. Obsolete. Also gated by CAP_SYS_MODULE. |
| delete_module | Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE. |
| finit_module | Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE. |
| get_kernel_syms | Deny retrieval of exported kernel and module symbols. Obsolete. |
| get_mempolicy | Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE. |
| init_module | Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE. |
| ioperm | Prevent containers from modifying kernel I/O privilege levels. Already gated by CAP_SYS_RAWIO. |
| iopl | Prevent containers from modifying kernel I/O privilege levels. Already gated by CAP_SYS_RAWIO. |
| kcmp | Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE. |
| kexec_file_load | Sister syscall of kexec_load that does the same thing, slightly different arguments. Also gated by CAP_SYS_BOOT. |
| kexec_load | Deny loading a new kernel for later execution. Also gated by CAP_SYS_BOOT. |
| keyctl | Prevent containers from using the kernel keyring, which is not namespaced. |
| lookup_dcookie | Tracing/profiling syscall, which could leak a lot of information on the host. Also gated by CAP_SYS_ADMIN. |
| mbind | Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE. |
| mount | Deny mounting, already gated by CAP_SYS_ADMIN. |
| move_pages | Syscall that modifies kernel memory and NUMA settings. |
| name_to_handle_at | Sister syscall to open_by_handle_at. Already gated by CAP_SYS_NICE. |
| nfsservctl | Deny interaction with the kernel nfs daemon. Obsolete since Linux 3.1. |
| open_by_handle_at | Cause of an old container breakout. Also gated by CAP_DAC_READ_SEARCH. |
| perf_event_open | Tracing/profiling syscall, which could leak a lot of information on the host. |
| personality | Prevent container from enabling BSD emulation. Not inherently dangerous, but poorly tested, potential for a lot of kernel vulns. |
| pivot_root | Deny pivot_root, should be privileged operation. |
| process_vm_readv | Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE. |
| process_vm_writev | Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE. |
| ptrace | Tracing/profiling syscall, which could leak a lot of information on the host. Already blocked by dropping CAP_PTRACE. |
| query_module | Deny manipulation and functions on kernel modules. Obsolete. |
| quotactl | Quota syscall which could let containers disable their own resource limits or process accounting. Also gated by CAP_SYS_ADMIN. |
| reboot | Don’t let containers reboot the host. Also gated by CAP_SYS_BOOT. |
| request_key | Prevent containers from using the kernel keyring, which is not namespaced. |
| set_mempolicy | Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE. |
| setns | Deny associating a thread with a namespace. Also gated by CAP_SYS_ADMIN. |
| settimeofday | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
| socket, socketcall | Used to send or receive packets and for other socket operations. All socket and socketcall calls are blocked except communication domains AF_UNIX, AF_INET, AF_INET6, AF_NETLINK, and AF_PACKET. |
| stime | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
| swapon | Deny start/stop swapping to file/device. Also gated by CAP_SYS_ADMIN. |
| swapoff | Deny start/stop swapping to file/device. Also gated by CAP_SYS_ADMIN. |
| sysfs | Obsolete syscall. |
| _sysctl | Obsolete, replaced by /proc/sys. |
| umount | Should be a privileged operation. Also gated by CAP_SYS_ADMIN. |
| umount2 | Should be a privileged operation. Also gated by CAP_SYS_ADMIN. |
| unshare | Deny cloning new namespaces for processes. Also gated by CAP_SYS_ADMIN, with the exception of unshare –user. |
| uselib | Older syscall related to shared libraries, unused for a long time. |
| userfaultfd | Userspace page fault handling, largely needed for process migration. |
| ustat | Obsolete syscall. |
| vm86 | In kernel x86 real mode virtual machine. Also gated by CAP_SYS_ADMIN. |
| vm86old | In kernel x86 real mode virtual machine. Also gated by CAP_SYS_ADMIN. |
2. 不使用默认的 seccomp 配置文件
可以传递 unconfined 以运行没有默认 seccomp 配置文件的容器。
$ docker run --rm -it --security-opt seccomp=unconfined debian:jessie \
unshare --map-root-user --user sh -c whoami