On 01/25/2016 12:54 PM, Jeffrey Ross wrote:
On 01/25/2016 06:55 AM, Jeffrey Ross wrote:
I'm in the process of setting up an SSH jail, for the most part its
working as expected with one exception, I want to provide access to
/dev/ttyUSB0 through /dev/ttyUSB4 (not 2) via cu.
When I attempt to use "cu -lttyUSB0 -s9600" I always get "line in use"
even through it is not in use and from another account not restricted to
the "jail" I can successfully connect to the ttyUSB0.
I've tried creating $chroot/
run/
lock/
lockdev/
uucp/
var/
run -> symbolic link to $chroot/run
lock -> symbolic link to $chroot/run/lock
and then matched the directory permissions so they are the same as the
"real" system.
ls -l $chroot/dev/ttyUSB?
crwxrwxrwx 1 root dialout 188, 0 Jan 24 14:48 ttyUSB0
crwxrwxrwx 1 root dialout 188, 1 Jan 24 14:49 ttyUSB1
crwxrwxrwx 1 root dialout 188, 3 Jan 24 14:49 ttyUSB3
crwxrwxrwx 1 root dialout 188, 4 Jan 24 14:49 ttyUSB4
The dialout group is 18 and the user is in group 18, initially I set the
permissions for the ttyUSB? to 660 before changing it to 777 as a last
ditch effort.
The "real" /dev/ttyUSB? -
ls -l /dev/ttyUSB?
crw-rw---- 1 root dialout 188, 0 Jan 24 14:44 /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 1 Jan 23 21:48 /dev/ttyUSB1
crw-rw---- 1 root dialout 188, 3 Jan 24 15:12 /dev/ttyUSB3
crw-rw---- 1 root dialout 188, 4 Jan 23 21:48 /dev/ttyUSB4
I'm probably missing something simple and any suggestions would be
appreciated.
Uhm, double check the permissions on the $chroot/var/run and
$chroot/var/lock directories and make sure that the user you're trying
to run as has write permissions in those directories. It's been a
while, but IIRC the only way cu can determine if a device is in use is
by checking the lock files and if it can't create a lock file, it says
the device is in use.
Why in the devil would you pull out that ancient program anyway? Man!
I haven't even LOOKED at cu/uucp in 15 years at least!
Just in case the permissions were wrong I did a chmod -R 777 on the run
directory, no dice, so I did the next best thing, I ran "strace -ff -o
outfile cu -l...." found a few libraries I missed, not sure if that was
part of the issue as that's not where the failure occurred. I did find
that it forked (?) lockdev which is a program that I had not included
$chroot, so I brought that program over into $chroot/usr/sbin/lockdev set
the permission appropriately and everything began working.
Why did I choose "cu" I know uucp is ancient but for a quick and dirty
way to connect to various serial interfaces cu seems to work well, and
although the remainder of the uucp suite comes with cu I did not configure
uucp :)
If you've got a suggestion for another program to use that will allow
quick connectivity to various serial ports I'm all ears.
How about minicom? Much more flexible.
You could have done an "ldd `which cu`" to find out what libraries it
uses, as well:
[root@prophead ~]# ldd `which cu`
linux-vdso.so.1 (0x00007fff015e3000)
liblockdev.so.1 => /lib64/liblockdev.so.1 (0x00007fee0c1f5000)
libnsl.so.1 => /lib64/libnsl.so.1 (0x00007fee0bfdc000)
libc.so.6 => /lib64/libc.so.6 (0x00007fee0bc1b000)
/lib64/ld-linux-x86-64.so.2 (0x000055a6208a4000)
However, running anything in a chroot jail is always sort of a problem.
Thanks!
Jeff
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- To err is human, to forgive is beyond the scope of the OS -
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