我在 ubuntu 17.04 主机上运行一个 centos7 非特权 LXD 容器。如果它在非特权模式下运行，我在容器内为 NOFILE 设置 ulimit 时遇到问题。
下面是重现的步骤：
$ lxc launch images:centos/7/amd64 mycontainer
$ lxc exec mycontainer bash
[root@mycontainer ~]# yum install strace
[root@mycontainer ~]# ulimit -n 200000
bash: ulimit: open files: cannot modify limit: Operation not permitted
[root@mycontainer ~]#
[root@mycontainer ~]# strace -e setrlimit bash -c 'ulimit -n 200000'
setrlimit(RLIMIT_NOFILE, {rlim_cur=200000, rlim_max=200000}) = -1 EPERM (Operation not permitted)
bash: line 0: ulimit: open files: cannot modify limit: Operation not permitted
+++ exited with 1 +++
[root@mycontainer ~]#
容器的配置细节：
$ sudo lxc config show mycontainer
architecture: x86_64
config:
image.architecture: amd64
image.build: "20170504_02:16"
image.description: Centos 7 (amd64) (20170504_02:16)
image.distribution: centos
image.release: "7"
volatile.base_image: 41c7bb494bbdf71c2aee471bb44a2318fd3424a0cd22091fb896a7614ae545eb
volatile.eth0.hwaddr: 00:16:3e:61:e4:6c
volatile.eth0.name: eth0
volatile.idmap.base: "0"
volatile.idmap.next: '[{"Isuid":true,"Isgid":false,"Hostid":140000,"Nsid":0,"Maprange":65536},{"Isuid":false,"Isgid":true,"Hostid":140000,"Nsid":0,"Maprange":65536}]'
volatile.last_state.idmap: '[{"Isuid":true,"Isgid":false,"Hostid":140000,"Nsid":0,"Maprange":65536},{"Isuid":false,"Isgid":true,"Hostid":140000,"Nsid":0,"Maprange":65536}]'
volatile.last_state.power: STOPPED
volatile.root.hwaddr: 00:16:3e:6b:93:1d
volatile.root.name: eth1
devices: {}
ephemeral: false
profiles:
- default
作为一种解决方法，我可以使容器具有特权，但我更喜欢只授予此容器的 rlimit 访问权限，或者能够从 lxd 提高限制。以下是我如何获得特权：
$ lxc config set mycontainer security.privileged true
$ lxc restart mycontainer
$ sudo lxc config show mycontainer
architecture: x86_64
config:
image.architecture: amd64
image.build: "20170504_02:16"
image.description: Centos 7 (amd64) (20170504_02:16)
image.distribution: centos
image.release: "7"
security.privileged: "true"
volatile.base_image: 41c7bb494bbdf71c2aee471bb44a2318fd3424a0cd22091fb896a7614ae545eb
volatile.eth0.hwaddr: 00:16:3e:61:e4:6c
volatile.eth0.name: eth0
volatile.idmap.base: "0"
volatile.idmap.next: '[]'
volatile.last_state.idmap: '[]'
volatile.last_state.power: RUNNING
devices: {}
ephemeral: false
profiles:
- default
