I ran into an issue with entries from limits.conf being affected when users default shell switched from csh to ksh. Once the switch was made the user lost the nofile and nproc settings. I ran an strace for both shells (edit passwd and strace -o"file" su - "account") and it shows both sessions reading the limits file and picking up the changes

strace line showing modified nofile limits being set

setrlimit(RLIMIT_NOFILE, {rlim_cur=1024, rlim_max=64*1024}) = 0

The above line along with the nproc settings appear to be picked up with both shells but when ksh is default shell.... actually anything but csh... it appears the new setting is not inherited by the shell. It is set to 8k not 64k

The kernel level is 2.6.18-238.19.1.0.1.el5 x86_64 I am at a loss for this one