On Wed, 2005-03-02 at 17:47 +0530, Reddy V, Ravinder (Ravinder) wrote: > Hi, > > Can anyone please let me know the system variable which holds the pseudo > terminal limit in fedora linux. > Also please let me know the filename where this variable is present, and how > to change this variable value? If you look in Documentation/devices.txt in the kernel sources, you will see that device major numbers 136-143 reserved for Unix98 pseudo-TTY devices. That makes 8 x 256 total available under the current device allocation scheme. However, if you look in include/linux/tty.h you see this: #define NR_UNIX98_PTY_DEFAULT 4096 /* Default maximum for Unix98 ptys */ #define NR_UNIX98_PTY_MAX (1 << MINORBITS) /* Absolute limit */ and in include/linux/kdev_t.h #define MINORBITS 20 Which gives a maximum of 1048576. So then looking in drivers/char/pty.c /* Unix98 devices */ #ifdef CONFIG_UNIX98_PTYS /* * sysctl support for setting limits on the number of Unix98 ptys allocated. * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. */ int pty_limit = NR_UNIX98_PTY_DEFAULT; static int pty_limit_min = 0; static int pty_limit_max = NR_UNIX98_PTY_MAX; And from sysctl: kernel.pty.max = 4096 So you can set it either by echoing a value into: /proc/sys/kernel/pty/max Or by using sysctl -w kernel.pty.max=<value> If you want to set it permanently, add a line to /etc/sysctl.conf and it will get loaded at boot time. -- C. Linus Hicks <lhicks at nc dot rr dot com>
