Tiny Core Linux
Tiny Core Base => TCB Q&A Forum => Topic started by: Lee on December 01, 2012, 03:27:41 PM
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Update 2012-12-14 1807: Changed subject to better reflect the issue. Original Subject was
The system has no more ptys. Ask your system administrator to create more.
Marked as [SOLVED] since the functionality now works (with sudo).
I'm trying to use an "expect script to send a simple command to a remote box via ssh. The script looks like this:
#!/usr/local/bin/expect
# whack871 - log in to the cisco 871 and warm boot it entirely under script
# control.
#
# set Variables from arguments
set ipaddr [lrange $argv 0 0]
set user [lrange $argv 1 1]
set password [lrange $argv 2 2]
set command [lrange $argv 3 3]
#
set arg1 [lrange $argv 4 4]
set timeout -1
#
# connect to remote ssh server (ipaddr) with given command to execute
spawn ssh $user@$ipaddr $command $arg1
match_max 100000
#
# Look for password prompt
expect "*?assword:*"
#
# Send password aka $password
send -- "$password\r"
#
# send blank line (\r) to make sure we get back to gui
send -- "\r"
expect eof
and is invoked like this:
whack871 <IP ADDRESS> <USERNAME> <PASSWORD> <COMMAND>
with command in quotes if it contains spaces.
but it results in this:
spawn ssh tc@192.168.0.97 xtrlock
The system has no more ptys. Ask your system administrator to create more.
while executing
"spawn ssh $user@$ipaddr $command $arg1"
(file "/home/tc/bin/whack871" line 18)
Under Cygwin on Windows Server 2008 R2, I can use this to warmboot my router.
Under Core 4.7.1, I cannot use this to send a command to another Core 4.7.1 box. Booting the local box with the multivt boot code does not seem to help.
I have openssh.tcz, expect.tcz and tcl.tcz loaded and I can ssh to the remote box.
Does anyone know how to add more ptys ?
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Try the boot code 'pty.legacy_count=32'
---- Edit ----
I tried it. It looks like legacy ptys are not enabled in the kernel.
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Thanks gerald_clark.
I was hoping for a simple boot code solution and it looks like that would have been it.
I'll look for a work around using something other than "spawn" - maybe something with exec and redirection. If that doesn't work, is there any down-side that you know of to enabling legacy ptys in the kernel?
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What is output of
cat /proc/sys/kernel/pty/maxand of
watch -n 1 cat /proc/sys/kernel/pty/nrjust at the moment you get the error?
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cat /proc/sys/kernel/pty/max
says 4096
watch -n 1 cat /proc/sys/kernel/pty/nr
shows an unchanging 2
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Could you check for same on target machine?
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On the target machine it is pretty much the same, except
watch -n 1 cat /proc/sys/kernel/pty/nr
shows 6
This number reflects the number of terminal windows open - it goes up as I open additional ssh sessions - which is really what I want the expect script to do anyhow. I wonder if I can replace that spawn command with something else.
When I run the watch command on the remote box and run the expect script on the remote box, it is exactly as when I run them on the local box.
When I run the watch command on the remote box and the expect script on the local box, the watched value still does not change.
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Expect should work fine with current PTYs. In fact, when I run your script here, it works as is.
I wonder if something is changing your permissions, on the host where you run expect. What's your permissions for /dev/ptmx and /dev/pty?
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tc@apollo:~$ ls -l /dev/ptmx /dev/pty
ls: /dev/pty: No such file or directory
crw-rw-rw- 1 root staff 5, 2 Dec 2 09:13 /dev/ptmx
tc@apollo:~$
tc@apollo:~$
tc@apollo:~$ ls -l /dev/ptmx /dev/pty?
ls: /dev/pty?: No such file or directory
crw-rw-rw- 1 root staff 5, 2 Dec 2 09:13 /dev/ptmx
tc@apollo:~$
This is with the multivt boot code that I added in yesterday:
tc@apollo:~$ cat /proc/cmdline
quiet host=cruzr0 noutc tz=GMT+5 tce=LABEL=cruzr0/boot/core4.7.1/tce waitusb=30:LABEL=cruzr0 multivt
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Typo, /dev/pts not pty.
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Ok then. I was a little worried for a minute there. :)
tc@apollo:~$ ls -l /dev/ptmx /dev/pts
crw-rw-rw- 1 root staff 5, 2 Dec 2 11:27 /dev/ptmx
/dev/pts:
total 0
crw------- 1 tc staff 136, 0 Dec 2 11:27 0
c--------- 1 root root 5, 2 Dec 1 09:54 ptmx
tc@apollo:~$
The mention of permissions gave me the idea to try the whole thing using sudo... and that worked, though I had to tweak my script a bit to be able to pass arguments to the remote command.
Still, it seems like it ought to be able to do this as non-root.
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Sorry, I mean the pts dir itself - "ls -lhd /dev/pts".
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tc@apollo:~$ ls -lhd /dev/pts
drwxr-xr-x 2 root root 0 Dec 1 09:54 /dev/pts/
tc@apollo:~$
Looks like only root can write to the directory...
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Why would you want to write to that directory?
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So it seems like that error msg is misleading and comes down to a permission issue.
BTW, just wondering, have you considered key authentification rather than using password?
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Why would you want to write to that directory?
I have no idea - just supposing something needs to be created there when the expect "spawn" command runs.
BTW, just wondering, have you considered key authentification rather than using password?
Yes, I may move to key authentication at some point.
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Hm, those permissions look ok. I'm afraid I don't know why expect fails for you, while you can still launch new terminals fine (they use the same mechanism).