unix
8 minUnix process inheritance: environment variables and file descriptors
Trace what survives fork and exec, and close capabilities a child should not inherit.
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7 matching resultsArticles and interview answers
unix
18 minLinux Under Load: Epoll, File Descriptors, OOM, TCP Queues, and VFS
Connect kernel readiness APIs, resource limits, cgroups, socket queues, page cache, and inode behavior to production symptoms.
unix
8 minUnix Foundations: File Permissions, Ownership, and Descriptors
Understand users, groups, permission bits, file descriptors, and redirection so shell and service behavior is easier to debug.
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Q&AWhat happens when a Java service creates too many threads?
Native stack memory, scheduling overhead, context switching, and file descriptors can be exhausted.
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Each platform thread consumes native resources, including stack reservation, and excessive runnable threads add scheduling and context-switching overhead. The service may hit native-thread creation errors or degrade before that point. Bound executors, measure queue depth and task latency, and apply backpressure rather than creating one thread per unbounded unit of work.
Q&A
Q&AWhat can a subprocess inherit across exec?
Environment strings and open descriptors not marked close-on-exec.
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Construct a deliberate environment and descriptor allowlist. Descriptors grant capabilities to files, sockets, or pipes; inherited writers can delay EOF and inherited secrets can leak to less-trusted children.
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Q&AWhy can epoll handle many mostly-idle sockets more efficiently than select?
epoll tracks interest and reports readiness changes instead of requiring repeated full-set scans.
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select requires rebuilding and scanning descriptor sets on each wait and has platform-specific descriptor limits; poll also examines a supplied list. epoll maintains kernel-side interest and ready structures, which suits large mostly-idle sets. It does not remove per-connection memory costs, application scheduling, or edge-triggered drain requirements.
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Q&AWhat does atomic file replacement leave unchanged for existing readers?
An already open descriptor still refers to the old file object.
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Write a complete temporary file on the same filesystem and replace the pathname. New opens see the replacement; existing descriptors keep the old object. Durability and concurrent-writer coordination are separate guarantees.