Writable Namespace Kernel Parameters ​

• Writable Namespace Kernel Parameters

Function Description ​

For services running in containers, such as databases, big data, and common applications, some kernel parameters need to be set and adjusted to obtain the optimal performance and reliability. The modification permission of all kernel parameters must be disabled or enabled simultaneously (by using privileged container).

When the modification permission is disabled, only the --sysctl external interface is provided and parameters cannot be flexibly modified in a container.

When the modification permission is enabled, some kernel parameters are globally valid. If some parameters are modified in a container, all programs on the host will be affected, harming security.

System containers provide the --ns-change-opt parameter, which can be used to dynamically set namespace kernel parameters in a container. The parameter value can be net or ipc.

Parameter Description ​

Constraints ​

• If both --privileged (privileged container) and --ns-change-opt are specified during container startup, --ns-change-opt does not take effect.

Example ​

Start a container and set --ns-change-opt to net.

[root@localhost ~]# isula run -tid --ns-change-opt net --system-container --external-rootfs /root/myrootfs none init
4bf44a42b4a14fdaf127616c90defa64b4b532b18efd15b62a71cbf99ebc12d2
[root@localhost ~]# isula exec -it 4b mount | grep /proc/sys
proc on /proc/sys type proc (ro,nosuid,nodev,noexec,relatime)
proc on /proc/sysrq-trigger type proc (ro,nosuid,nodev,noexec,relatime)
proc on /proc/sys/net type proc (rw,nosuid,nodev,noexec,relatime)

The mount point /proc/sys/net in the container has the rw option, indicating that the net-related namespace kernel parameters have the read and write permissions.

Start another container and set --ns-change-opt to ipc.

[root@localhost ~]# isula run -tid --ns-change-opt ipc --system-container --external-rootfs /root/myrootfs none init
c62e5e5686d390500dab2fa76b6c44f5f8da383a4cbbeac12cfada1b07d6c47f
[root@localhost ~]# isula exec -it c6 mount | grep /proc/sys
proc on /proc/sys type proc (ro,nosuid,nodev,noexec,relatime)
proc on /proc/sysrq-trigger type proc (ro,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/shmmax type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/shmmni type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/shmall type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/shm_rmid_forced type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/msgmax type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/msgmni type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/msgmnb type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/kernel/sem type proc (rw,nosuid,nodev,noexec,relatime)
proc on /proc/sys/fs/mqueue type proc (rw,nosuid,nodev,noexec,relatime)

The mount point information of ipc-related kernel parameters in the container contains the rw option, indicating that the ipc-related namespace kernel parameters have the read and write permissions.