170. tcsh in ROCKS/CentOS with hardcoded csh.cshrc path

WHAT THIS POST DOES: It shows you how to compile your own tcsh which won't be looking at /etc/csh.cshrc. It doesn't show you how to set up the correct .cshrc files. But it certainly allows you to experiment.

Also, keep in mind that since each local node hdd has it's own /bin directory (not exported) you need to make similar changes on each node (i.e. change the /bin/csh symlink -- see below)

(The) csh (startup files) is(are) horribly broken on ROCKS 5.4.3.

For now I've solved it by just moving  /etc/csh.cshrc out of the way, but what we do here is symlink /bin/csh to our own tcsh which been hardcoded to use a non-standard configuration file, so that you can use the standard ROCKS tcsh with /etc/csh.cshrc and your own csh(tcsh) with your own config files.

To be clear: it's not the csh binary which is borked on ROCKS 5.4.3, but the configuration files.

There's a patch for the broken csh -- but when I applied it to a test computer it only got broken-er and prevented the csh from opening and staying open. Good way of getting locked out. So I'm not keen on doing the same thing on someone else's production cluster. Also, I've opted for tcsh since the csh sources come with a bsd style makefile, and I really can't deal with that right now.

What we'll do is hardcode the location of the csh.cshrc file and change it from /etc/csh.cshrc to /share/apps/utils/tcsh

sudo mkdir /share/apps/utils
sudo chown ${USER} /share/apps/utils
cd /share/apps/utils
 wget http://ftp.de.debian.org/debian/pool/main/t/tcsh/tcsh_6.18.01.orig.tar.gz
tar xvf tcsh_6.18.01.orig.tar.gz
 cd tcsh-6.18.01/

Time for find out what to change:
tail -n 9999 *|strings|egrep "/etc/csh.cshrc|<=="


tells us we need to have a look at pathnames.h
Change

124 # define _PATH_DOTCSHRC     "/etc/csh.cshrc"
to
124 # define _PATH_DOTCSHRC     "/share/apps/utils/custom.tcshrc"

./configure --prefix=/share/apps/utils/tcsh
make
make install

If all went well:
cat tcsh|strings|grep custom.tcsh

/share/apps/utils/custom.tcshrc

and

tree /share/apps/utils/tcsh -L 1
/share/apps/utils/tcsh
|-- bin
`-- share

Obviously, this doesn't really make much of a difference just yet. Now comes the scary part -- and you need root access for this:
 which csh

/bin/csh

ls /bin/csh -lah

lrwxrwxrwx 1 root root 4 Feb 23 16:54 /bin/csh -> tcsh

and here's the 'dangerous' stuff:
sudo rm /bin/csh
sudo ln -s /share/apps/utils/bin/tcsh /bin/csh

sudo chown root:root /bin/csh
sudo chmod 777 /bin/csh

Since /bin/csh isn't a binary but a symmlink to tcsh in the /bin directory, we just delete the symlink and create a new one.

We can now make whatever changes we want to our custom.tcshrc while still being able to easily change back to the old setup. I do recognise that we could just have edited /etc/csh.cshrc and /login.cshrc, but I for some reason feel a lot more comfortable using this method.