Q6.1 Setuid scripts don't seem to work. Q6.2 Free memory as reported by free keeps shrinking. Q6.3 When I add more memory it slows to a crawl. Q6.4 Some programs (e.g. xdm) won't let me log in.
Q6.5 Some programs let me log in with no password. Q6.6 My machine runs very slowly when I run GCC / X / ... Q6.7 I can only log in as root. Q6.8 My screen is all full of weird characters instead of letters. Q6.9 I have screwed up my system and can't log in to fix it. Q6.10 Emacs just dumps core. Q6.11 I've discovered a huge security hole in rm ! Q6.12 lpr and/or lpd aren't working.
That's right. This feature has been deliberately disabled in the Linux kernel because setuid scripts are almost always a security hole. If you want to know why read the FAQ for comp.unix.questions.
Question 6.2. Free memory as reported by free keeps shrinking.
The `free' figure printed by free doesn't include memory used as a disk buffer cache - shown in the `buffers' column. If you want to know how much memory is really free add the `buffers' amount to `free'.
The disk buffer cache tends to grow soon after starting Linux up, as you load more programs and use more files and the contents get cached. It will stabilise after a while.
Question 6.3. When I add more memory it slows to a crawl.
This is quite a common symptom of a failure to cache the additional memory. The exact problem depends on your motherboard.
Sometimes you have to enable caching of certain regions in your BIOS setup. Look in the CMOS setup and see if there is an option to cache the new memory area which is currently switched off. This is apparently most common on a 486.
Sometimes the RAMs have to be in certain sockets to be cached.
Sometimes you have to set jumpers to enable the caching.
Some motherboards don't cache all the RAM if you have more RAM per amount of cache than they expect. Usually a full 256K cache will solve this problem.
If in doubt, check your motherboard manual. If you still can't fix it because the documentation is inadequate you might like to post a message giving *all* the details - make, model number, date code, etc. so that other Linux users can avoid it.
Question 6.4. Some programs (e.g. xdm) won't let me log in.
You are probably using non-shadow-password programs but are using shadow passwords.
If so, you have to get or compile a shadow password version of the program(s) in question. The shadow password suite can be found in (amongst other places): tsx-11.mit.edu:/pub/linux/sources/usr.bin/shadow-* This is the source code; you will probably find the binaries in .../linux/binaries/usr.bin.
Question 6.5. Some programs let me log in with no password.
You probably have the same problem as in Q6.4 `Some programs (e.g. xdm) won't let me log in.', with an added wrinkle:
If you are using shadow passords you should put an asterisk in the password field of /etc/passwd for each account, so that if a program doesn't know about the shadow passwords it won't think it's a passwordless account and let anyone in.
Question 6.6. My machine runs very slowly when I run GCC / X / ...
You may not have any swap enabled. You need to enable swapping to allow Linux to page out bits of data programs aren't using at the moment to disk to make more room for other programs and data. If you don't Linux has to keep data in memory and throw away in-memory copies of programs (which are paged straight from the filesystem) and so less and less program is in memory and everything runs very slowly.
See the Installation HOWTO and the Installation and Getting Started Guide [Q2.1 `Where can I get the HOWTOs and other documentation ?
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