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| author | Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2016-02-21 10:06:14 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-03-07 16:11:14 -0800 |
| commit | 8b253b07e990ca453f31503aacb29004f2a87364 (patch) | |
| tree | 1b4ec23c3e2e71813a333d940e02fecc32c13c80 /Documentation/filesystems | |
| parent | 465893e18878e119d8d0255439fad8debbd646fd (diff) | |
| download | linux-8b253b07e990ca453f31503aacb29004f2a87364.tar.gz linux-8b253b07e990ca453f31503aacb29004f2a87364.tar.xz | |
TTY, devpts: document pty count limiting
Logic has been changed in kernel 3.4 by commit e9aba5158a80
("tty: rework pty count limiting") but still not documented.
Sysctl kernel.pty.max works as global limit, kernel.pty.reserve ptys
are reserved for initial devpts instance (mounted without "newinstance").
Per-instance limit also could be set by mount option "max=%d".
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/devpts.txt | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/filesystems/devpts.txt b/Documentation/filesystems/devpts.txt index 68dffd87f9b7..30d2fcb32f72 100644 --- a/Documentation/filesystems/devpts.txt +++ b/Documentation/filesystems/devpts.txt @@ -51,6 +51,15 @@ where 'ns_exec -cm /bin/bash' calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. +Total count of pty pairs in all instances is limited by sysctls: +kernel.pty.max = 4096 - global limit +kernel.pty.reserve = 1024 - reserve for initial instance +kernel.pty.nr - current count of ptys + +Per-instance limit could be set by adding mount option "max=<count>". +This feature was added in kernel 3.4 together with sysctl kernel.pty.reserve. +In kernels older than 3.4 sysctl kernel.pty.max works as per-instance limit. + User-space changes ------------------ |