MATLAB: Can’t I use the UNIX or ! commands in MATLAB 6.0 (R12) if I have an older Linux kernel

2.2.132.2.14MATLAB

When I start MATLAB, I get the following message although MATLAB does come up just fine.

 ---------------------------------------------------------------
 Warning: Linux 2.2.2 - your operating system
                  Linux 2.2.15 - MATLAB built using   
 this system
 ---------------------------------------------------------------
 ??? MATLAB was unable to open the 
 pseudo-tty master device /dev/ptmx. The unix()
 and ! commands will not work in this MATLAB 
 session. Other commands which depend 
 upon unix() and ! will fail. Please check with 
 your system administrator and confirm that 
 this device exists with the proper permissions.
 %

I just can't use UNIX or ! commands in MATLAB.

Best Answer

The warning about the different kernel versions can be ignored. We warn about this by default, but there are no significant differences between the two kernels that would cause any trouble.

The problem with UNIX and ! commands needs to be resolved on your part. Please see below for help on this.

MATLAB R12 relies on a working Unix98 pty setup. This was available on all the major distributions long before we shipped, though it's possible for someone who has upgraded piecemeal to have

missed this one.

Things to look for:

1. The device /dev/ptmx must exist and be writable.

 greg@fess 839$ ls -l /dev/ptmx
 crw-rw-rw-   1 root     tty        5,   2 Dec  1 17:28 /dev/ptmx

Use "mknod -m 666 /dev/ptmx c 5 2" to remedy.

2. The directory /dev/pts must exist

 greg@fess 840$ ls -ld /dev/pts
 drwxr-xr-x   2 root     root            0 Nov 13 09:11 /dev/pts/

Use "mkdir /dev/pts; chmod 755 /dev/pts" to remedy

3. The filesystem type "devpts" must be supported in the kernel

 greg@fess 841$ cat /proc/filesystems | grep pts
 nodev   devpts

Reconfigure and rebuild your kernel to remedy this.

4. The filesystem /dev/pts of type devpts must be mounted

 greg@fess 842$ cat /proc/mounts | grep pts
 devpts /dev/pts devpts rw 0 0

Short term remedy: "mount -t devpts devpts /dev/pts"

Long term remedy: put this into a startup script or add it to your /etc/fstab file.

There is plenty of info on the web to help you with any phase of this, depending on where you're falling short. One common failure mode seems to be this one:

******************

I've had some problems that stem from compiling a kernel (2.2.10) and not getting devpts included. I've searched throughout the kernel and haven't found this as an option, but when I compile and then boot from the new kernel, I get error messages on bootup that it has no support for filesystem devpts when mounting my disk's partitions.

Pts is a method of defining and accessing terminals. It has been included in newer version of Linux to work toward Unix98 branding.

Pts inclusion in the kernel is under 'Character Devices.' The help for that option recommends also adding the '/dev/pts filesystem for Unix98 PTYs' under 'Filesystems.' It sounds as if you've not done this latter step.

******************

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MATLAB: Does MATLAB crash on the Linux system with a System::_utException or System::SimpleException error

This error can occur when the pseudo terminal and serial interface devices (/dev/ptyp, /dev/pts, and/or /dev/ttyp) are not mounted, or are mounted without the proper permissions. This commonly occurs in CHROOT partitions as it is a protected environment. If you are using a CHROOT partition, see the related solution 1-1B3HE: "How do I run MATLAB inside a CHROOT partition?"

If MATLAB is not installed in a CHROOT partition and you are experiencing this error, check to see if /dev/pts is mounted on your system. To do so, simply run the command:

 mount

You should see a line with the following (or something similar)

 devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)

This will indicate that /dev/pts is mounted. If not, you can add the following line to your /etc/rc.local file:

 mount -t devpts devpts /dev/pts

Once complete, /dev/pts should be mounted the next boot.

Once mounted, try MATLAB again. If it still fails to start, try running MATLAB as root (if possible). If it starts normally, the permissions to the pty and tty devices may not be set correctly for users. You will need to refer to your specific distribution to find the proper permissions for these devices.

You may also be able to resolve this error by running the following command as root:

chmod o+rw /dev/ttyp* /dev/ptyp*

If you are still unable to start MATLAB after following these steps, contact installation support here:

http://www.mathworks.com/support/contact_us/index.html

MATLAB: How to run MATLAB inside a CHROOT partition

MATLAB has a set of dependencies that are different from Java and Perl. If you are running your shell in the confinement of a CHROOT environment, you need to make sure that these dynamic dependencies are made available. Furthermore, SIMULINK also has dependencies, some of which are different from those of MATLAB.

You can run LDD on MATLAB and SIMULINK in the $MATLAB/bin/$ARCH directory, where $MATLAB = the MATLAB root directory on your machine and $ARCH is you system architecture. The executable files for MATLAB and SIMULINK are "matlab" and "libmwsimulink.so".

In particular, if you are not allowed to access /dev/ptmx or other pty devices under the /dev directory, MATLAB will not be able to use the bang (!) operator to shell out of MATLAB and run arbitrary shell commands.

Also note that /dev and directories such as /dev/pts are "two" file systems, so you have to mount each explicitly onto the CHROOT partition. The following set of commands is what you use to set up the CHROOT environment:

 DIR=/data/rouquett/sandbox
 mount -r --bind /bin ${DIR}/bin
 mount -r --bind /lib ${DIR}/lib
 mount -r --bind /dev ${DIR}/dev
 mount -r --bind /dev/pts ${DIR}/dev/pts
 mount -r --bind /etc ${DIR}/etc
 mount -r --bind /export ${DIR}/export
 mount -r --bind /opt ${DIR}/opt
 mount -r --bind /proc ${DIR}/proc
 mount -r --bind /sbin ${DIR}/sbin
 mount --bind /tmp ${DIR}/tmp
 mount -r --bind /usr ${DIR}/usr
 mount -r --bind /var ${DIR}/var

For auto-mounted NFS volumes, you would have to do something like:

 mount -t nfs <server>:<path-to-home file system> ${DIR}/home

Best Answer

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