Move pages under tldr, lint run.sh, update docs

tldr/linux/nsenter

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+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# nsenter
+
+> Run a new command in a running process' namespace.
+> Particularly useful for docker images or chroot jails.
+> More information: <https://manned.org/nsenter>.
+
+- Run a specific command using the same namespaces as an existing process:
+
+`nsenter --target {{pid}} --all {{command}} {{command_arguments}}`
+
+- Run a specific command in an existing process's network namespace:
+
+`nsenter --target {{pid}} --net {{command}} {{command_arguments}}`
+
+- Run a specific command in an existing process's PID namespace:
+
+`nsenter --target {{pid}} --pid {{command}} {{command_arguments}}`
+
+- Run a specific command in an existing process's IPC namespace:
+
+`nsenter --target {{pid}} --ipc {{command}} {{command_arguments}}`
+
+- Run a specific command in an existing process's UTS, time, and IPC namespaces:
+
+`nsenter --target {{pid}} --uts --time --ipc -- {{command}} {{command_arguments}}`
+
+- Run a specific command in an existing process's namespace by referencing procfs:
+
+`nsenter --pid=/proc/{{pid}}/pid/net -- {{command}} {{command_arguments}}`