Zombie進程是已完成執(zhí)行但未被父進程回收的進程，因父進程未調(diào)用wait()讀取其狀態(tài)；它不占用資源但會占據(jù)進程表條目。Orphan進程是父進程先于子進程終止，子進程被init/systemd接管；它可正常運行直至結(jié)束。二者均非危險，但需注意：僵尸進程過多會耗盡進程表，需修復(fù)父進程代碼；孤兒進程若失控可能浪費資源，應(yīng)通過監(jiān)控確保其正確結(jié)束。

Zombie and orphan processes are two types of processes in Unix-like operating systems that behave differently when their parent or child processes terminate unexpectedly or without proper handling.

What Makes a Process a Zombie?

A zombie process, also known as a defunct process, is a process that has completed execution but still has an entry in the process table. This happens because the parent process hasn’t yet read its exit status using a wait() system call.

• The child process finishes running.
• It sends an exit signal (like SIGCHLD) to its parent.
• If the parent doesn’t call wait(), the child remains as a zombie.
• Zombies don’t use CPU or memory, but they do occupy a slot in the process table.

You might see zombie processes when checking with tools like top or ps, listed under a state of "Z". They’re not harmful in small numbers, but if you notice many zombies piling up, it could point to a bug or poor coding practice in the parent process.

How Do Orphan Processes Work?

An orphan process is a child process whose parent has terminated. When this happens, the child gets adopted by the init process (or systemd on modern Linux systems), which becomes its new parent.

Here’s what typically happens:

• The parent process exits before the child finishes.
• The child continues running independently.
• The operating system automatically re-parents the child to the init/systemd process.
• The orphaned process can still run normally and will be cleaned up once it exits.

Orphan processes aren't inherently bad — sometimes it's intentional, like when a background service is started and the user logs off. But if you're seeing unexpected or uncontrolled orphan processes, it may indicate a logic issue in how your application handles child processes.

Why Should You Care About These Processes?

While neither zombie nor orphan processes are dangerous on their own, understanding them helps with debugging and system maintenance.

For zombie processes:

• They can eventually fill up the process table, preventing new processes from starting.
• Fixing them usually involves updating or patching the parent process to properly call wait().

For orphan processes:

• They can consume system resources longer than expected if not managed correctly.
• Monitoring and logging help ensure these processes finish as intended.

In most cases, well-written applications and system services won’t leave behind too many zombies or cause unintended orphans. But knowing how these processes work gives you better control over troubleshooting and performance tuning.

That's basically how it works — not super complicated, but easy to overlook if you're not watching system behavior closely.

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