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Commit | Line | Data |
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eedf265a EB |
1 | Each mount of the devpts filesystem is now distinct such that ptys |
2 | and their indicies allocated in one mount are independent from ptys | |
3 | and their indicies in all other mounts. | |
784c4d8b | 4 | |
eedf265a EB |
5 | All mounts of the devpts filesystem now create a /dev/pts/ptmx node |
6 | with permissions 0000. | |
784c4d8b | 7 | |
eedf265a EB |
8 | To retain backwards compatibility the a ptmx device node (aka any node |
9 | created with "mknod name c 5 2") when opened will look for an instance | |
10 | of devpts under the name "pts" in the same directory as the ptmx device | |
11 | node. | |
784c4d8b | 12 | |
eedf265a EB |
13 | As an option instead of placing a /dev/ptmx device node at /dev/ptmx |
14 | it is possible to place a symlink to /dev/pts/ptmx at /dev/ptmx or | |
15 | to bind mount /dev/ptx/ptmx to /dev/ptmx. If you opt for using | |
16 | the devpts filesystem in this manner devpts should be mounted with | |
17 | the ptmxmode=0666, or chmod 0666 /dev/pts/ptmx should be called. | |
784c4d8b | 18 | |
8b253b07 KK |
19 | Total count of pty pairs in all instances is limited by sysctls: |
20 | kernel.pty.max = 4096 - global limit | |
eedf265a | 21 | kernel.pty.reserve = 1024 - reserved for filesystems mounted from the initial mount namespace |
8b253b07 KK |
22 | kernel.pty.nr - current count of ptys |
23 | ||
24 | Per-instance limit could be set by adding mount option "max=<count>". | |
25 | This feature was added in kernel 3.4 together with sysctl kernel.pty.reserve. | |
26 | In kernels older than 3.4 sysctl kernel.pty.max works as per-instance limit. |