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Q Setuid scripts dont seem to work Q Free memory as reported by free keeps shrinking Q When I add more memory it slows to a crawl Q Some programs (eg xdm) wont let me log in Q Some programs let me log in with no password Q My machine runs very slowly when I run GCC / X / Q I can only log in as root Q My screen is all full of weird characters instead of letters Q I have screwed up my system and cant log in to fix it Q Emacs just dumps core Q Ive discovered a huge security hole in rm ! Q lpr and/or lpd arent working Question Setuid scripts dont seem to work Thats 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 compunixquestions Question Free memory as reported by free keeps shrinking The `free figure printed by free doesnt 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 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 Sometimes the RAMs have to be in certain sockets to be cached Sometimes you have to set jumpers to enable the caching Some motherboards dont cache all the RAM if you have more RAM per amount of cache than they expect Usually a full K cache will solve this problem If in doubt check your motherboard manual If you still cant 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 Some programs (eg xdm) wont let me log in You are probably using nonshadowpassword 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): tsxmitedu:/pub/linux/sources/usrbin/shadow* This is the source code; you will probably find the binaries in /linux/binaries/usrbin Question Some programs let me log in with no password You probably have the same problem as in Q `Some programs (eg xdm) wont 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 doesnt know about the shadow passwords it wont think its a passwordless account and let anyone in Question 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 arent using at the moment to disk to make more room for other programs and data If you dont Linux has to keep data in memory and throw away inmemory 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 [Q `Where can I get the HOWTOs and other documentation ?] for details of how to set up a swap partition or swapfile; see also Q `My swap area isnt working Alternatively you may have too little real memory If you have less RAM than all the programs youre running at once use Linux will use your hard disk instead and thrash horribly The solution in this case is to not run so many things at once or to buy more memory You can also reclaim some memory by compiling and using a kernel with less options configured See Q `How do I upgrade/recompile my kernel ? You can tell how much memory and/or swap youre using by using the free command or by typing cat /proc/meminfo If your kernel is configured with a ramdisk this is probably wasted space and will cause things to go slowly Use LILO or rdev to tell the kernel not to allocate a ramdisk (see the LILO documentation or type man rdev) Question I can only log in as root You probably have some permission problems or you have a file /etc/nologin If the latter put rm f /etc/nologin in your /etc/rc or /etc/rclocal Otherwise check the permissions on your shell and any filenames which appear in error messages and also the directories containing these files all the way back up the tree to the root directory Question My screen is all full of weird characters instead of letters You probably sent some binary data to your screen by mistake Type echo ^V^[c (thats e c h o space controlV escape c return) to fix it Many Linux distributions have a command reset that does this Question I have screwed up my system and cant log in to fix it Reboot from an emergency floppy or floppy pair for example the Slackware boot and rootdisk pair (in the install subdirectory of the Slackware mirrors) or the MCC installation boot floppy There are also two diy rescue disk creation packages on sunsiteuncedu in /pub/Linux/system/Recovery These are better as theyll have your own kernel on them so that you dont run the risk of missing devices filesystems etc Get to a shell prompt and mount your hard disk with something like mount t ext /dev/hda /mnt Then your filesystem is available under the directory /mnt and you can fix the problem Remember to unmount your hard disk before rebooting (cd back down to / first or it will say its busy) |
