27 lines
1.3 KiB
Plaintext
27 lines
1.3 KiB
Plaintext
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Each mount of the devpts filesystem is now distinct such that ptys
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and their indicies allocated in one mount are independent from ptys
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and their indicies in all other mounts.
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All mounts of the devpts filesystem now create a /dev/pts/ptmx node
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with permissions 0000.
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To retain backwards compatibility the a ptmx device node (aka any node
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created with "mknod name c 5 2") when opened will look for an instance
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of devpts under the name "pts" in the same directory as the ptmx device
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node.
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As an option instead of placing a /dev/ptmx device node at /dev/ptmx
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it is possible to place a symlink to /dev/pts/ptmx at /dev/ptmx or
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to bind mount /dev/ptx/ptmx to /dev/ptmx. If you opt for using
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the devpts filesystem in this manner devpts should be mounted with
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the ptmxmode=0666, or chmod 0666 /dev/pts/ptmx should be called.
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Total count of pty pairs in all instances is limited by sysctls:
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kernel.pty.max = 4096 - global limit
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kernel.pty.reserve = 1024 - reserved for filesystems mounted from the initial mount namespace
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kernel.pty.nr - current count of ptys
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Per-instance limit could be set by adding mount option "max=<count>".
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This feature was added in kernel 3.4 together with sysctl kernel.pty.reserve.
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In kernels older than 3.4 sysctl kernel.pty.max works as per-instance limit.
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