htop 是 top 命令的一个变种，它提供了更多的交互性、定制性以及其他一些功能，但是它同时使用了相比 top 更多的资源（4 倍多的 syscalls）
top 命令常用选项
选项
说明
示例
-H
Threads Mode，线程模式。默认情况 top 展示进程的简要信息，使用此选项显示进程中的线程状态。 对应交互式命令 H
top 常用交互命令
命令
说明
P
CPU Utilization 排序，默认排序方式
M
Memory Utilization 排序
I
Irix/Solaris-Mode 切换。 默认为 Itrix Mode,在这种模式下，如果某个进程使用了系统中的 2 个 CPU 的所有计算资源，则其 CPU 使用率展示为 200%，依此类推。 在 Solaris Mode 下，进程的 CPU 使用率是整体 CPU 使用的资源除于 CPU 数。如在 4 CPU 的系统中，Itrix 模式下，进程 CPU 使用率为 200%，在 Solaris 模式下，则为 50%
IOPS Input/Output Operations Per Second. 用于衡量数据传输操作（Rate of Data transfer operations）的频率。对于硬盘 I/O （Disk I/O）来说，指 每秒发生的读写请求 。
Throughput 吞吐量 。在网络通信中，主要指 数据传输速率（Data Rate, bytes/bits per second） 。在其他上下文（Contexts,如 Databases），Throughput 通常指 Operation Rate（Operations Per Second or Transactions Per Second）
# systemd-analyze critical-chain The time when unit became active or started is printed after the "@" character. The time the unit took to start is printed after the "+" character.
UEFI 包含了一个平台相关（platform-related）的 数据表（data table） ，以及 可以被 OS Loader 调用的 Boot and Runtime Service Calls 。这些信息定义了为支持 UEFI ，固件（Firmwares）或者计算机硬件（Hardwares）应该实现的接口和数据结构（Interfaces and Structures）。
PAM 中的 Control Flags 用于决定返回什么样的状态。下表列出了 PAM 配置中的相关的 Control Flags 及其响应
Control Flag
Response Handle
required
If failed, returns a failure status to the application, after the rest of the contexts have been run in the stack. For example, a requisite control might cause a login to fail if someone types in an invalid user. But the user might not be told of the failure until after entering a password, hiding the fact that it was the bad username that caused the failure
requisite
If failed, returns a failure status to the application immediately without running the rest of the stack 。 (Be careful where you place this control in the stack.) For example, a requisite control might require key-based authentication and fail immediately when a valid key is not provided . In that case, it could fail before even prompting for a username/password.
sufficient
- If failed, the module status is ignored. - If successful, then a success status is immediately returned to the application without running the rest of the stack. (Be careful where you place this control in the stack.)
optional
This control flag is important only for the final overall return status of success or failure . Think of it as a tiebreaker. When the other modules in the configuration file stack return statuses that are neither clear-cut failure nor success statuses, this optional module’s status is used to determine the final status or break the tie. In cases where the other modules in the stack are returning a clear-cut path of failure or success, this status is ignored.
include
Get all the return statuses from this particular PAM configuration file’s stack to include in this stack’s overall return status. It’s as if the entire stack from the named configuration file is now in this configuration file
substack
Similar to the include control flag, except for how certain errors and evaluations affect the main stack. This forces the included configuration file stack to act as a substack to the main stack. Thus, certain errors and evaluations affect only the substack and not the main stack.
