Stupid things on Unix/Linux
| SYMPTOMS | POSSIBLE CAUSE | POSSIBLE SOLUTION |
| While using vi on a remote unix machine, occasionally (but just too often to be workable) your cursor movements are ignored, instead strange characters are inserted into your text. | don't know. Maybe some environment variable? | Start an xterm on the remote machine (don't forget to set the DISPLAY to your own terminal) and use the new window for vi. |
| YP_BINDPROC: domain not bound | This vague error indicates that the automounter fails. This means that you don't have access to your files on the fileserver, and therefore that you cannot do anything - even not log in - as you usually have don't any access rights on the local file system. |
If you have root access: log in as root, and type cd /etc/rc.d/init.d. Then type ./amd stop; ./ypbind stop; ./ypbind start; .amd start. If this still fails try to ping to the fileserver and check"lsmod" to check whether the network driver has been loaded. If you don't have root access: check if the fileserver is up, and if so reboot your system (ctrl-alt-delete) and hope the best. After 2 or 3 failures I would think it's time to reboot the file server itself... |
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You get "host or gateway not responding: | rsh may be disabled because of security reasons | Use ssh instead. |
| You cannot remote log in to a linux machine that you have an account on | The machine you try to login from is not mentioned in the file /etc/hosts.allow and/or in $(HOME)/.rhosts | Enter the machinename or number in these files, and type /ets/rc.d/init.d/inet restart (you need to be root to change /etc/hosts.allow) |
| vi uses only part of your window. Scrolling does not work OK | the window size that vi assumes does not match the actual window size | type "eval `resize`" in your xterm. Note the backquotes around resize. |
| Using arrow keys in vi sometimes causes strange characters to be inserted. | Probably some network congestion problems |
start vi in a remote window instead of a local window. To do this, type on your local machine xhost remote_machine_name rsh remote_machine_name setenv DISPLAY local_machine_name:0.0 xterm & and now use the new window that appears after the xterm command. |
| How to replace carriage returns with newlines in vi | somehow the carriage returns cannot be found? |
It seems that carriage returns are found also when searching for newlines. Try the following set noai vi <filename> :s/<ctrl-v><enter>/<ctrl-v><enter>/g<enter> |
| How to turn off automatic replies on mails that you're on holiday (turn this on with making a "vacation.msg" file containing your message and giving the command "vacation -i") | The suggestion of touching the vacation.msg file does not work on the SGI I worked on. | remove the .forward file |
| You have a table with multiple columns, and pictures with "width=100%" in the cells. The images are scaled at full-page size instead of full-column size when the page is opened, and scaled at column-size only after the window is resized. | Bug in Netscape? It is not clear whether this is proper use of html. | See my tip on this problem on my mac tips page. |
| g++ compiler message "undefined reference to `XXX virtual table'" | The class XXX has some virtual function(...) that has not been implemented |
make function pure virtual by appending "=0", thus virtual function(...)=0; or implement the function. A good point from C++ FAQs Lite: Many compilers put this magical "virtual table" in the compilation unit that defines the first non-inline virtual function in the class. Thus if the first non-inline virtual function in Fred is wilma(), the compiler will put Fred's virtual table in the same compilation unit where it sees Fred::wilma(). Unfortunately if you accidentally forget to define Fred::wilma(), rather than getting a Fred::wilma() is undefined, you may get a "Fred's virtual table is undefined". |
| shmget succeeds only when requested very small chunks, for instance it may fail when more than 1Mb is requested while the manuals indicate that the limit is 8 blocks of 4Mb = 32Mb. This problem occurs both in Linux2.0.34 and on SGI Irix6.4. | shmget seems very sensitive to the specific key given. If you use ftok to create the key (for instance I saw key=ftok(".",'M') in some example program), the amount of available shared memory may even depend on the specific directory where the program is run. | Use a path referring to some stable file, eg "/tmp". I'm not sure whether this solves all problems. |
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g++ compiler message "In method XXX const blablabla" | The class is defined const (ie it does not change the object) and therefore the functions it calls have to be const as well | Check whether this function really will not change the object. |
| g++ warning "trigraph(s) encountered" | You have in your source code a string starting with two question marks, such as ??= or ??!. These are shortcuts for special characters in ANSI C (see here or K&R page 296?) | Replace these with their single-characters equivalent or remove them altogether. (you need -pedantic option with gcc to compile trigraphs). (Thank you Vijo for additional info). |
| Java comes with message: Exception in thread "main" java.lang.UnsatisfiedLinkError: /home/wouter/workspace/Interpreter/bugfix_prolog/foreignframe/libforeign.so: Can't load IA 32-bit .so on a IA 32-bit platform | Java seems to catch a lower-level exception and translates it into this stupid message. What usually is the case is that there is an unresolved link during loading a native c library. Apparently you need to set the LD_LIBRARY_PATH environment var to point to the .so files. Sometimes explicit linking is needed as well. | Make sure the LD_LIBRARY_PATH var points to the .so files needed. Furthermore. Turn on the java debugger with "setenv LD_DEBUG libs" and re-run the java program. This time you get lots of debug output. Locate the first error message above the failure. |