Section 6. Solutions to common miscellaneous prob

　　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)
　　
　　
From:http://tw.wingwit.com/Article/program/Oracle/201311/18664.html