keyctl: add page (#7160)

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pages/linux/keyctl.md

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+# keyctl
+
+> Manipulate the Linux kernel keyring.
+> More information: <https://manned.org/keyctl>.
+
+- List keys in a specific keyring:
+
+`keyctl list {{target_keyring}}`
+
+- List current keys in the user default session:
+
+`keyctl list {{@us}}`
+
+- Store a key in a specific keyring:
+
+`keyctl add {{type_keyring}} {{key_name}} {{key_value}} {{target_keyring}}`
+
+- Store a key with its value from standard input:
+
+`echo -n {{key_value}} | keyctl padd {{type_keyring}} {{key_name}} {{target_keyring}}`
+
+- Put a timeout on a key:
+
+`keyctl timeout {{key_name}} {{timeout_in_seconds}}`
+
+- Read a key and format it as a hex-dump if not printable:
+
+`keyctl read {{key_name}}`
+
+- Read a key and format as-is:
+
+`keyctl pipe {{key_name}}`
+
+- Revoke a key and prevent any further action on it:
+
+`keyctl revoke {{key_name}}`