gww@aphasia.UUCP (George Williams) (08/27/85)
We have here a callan box (modified by someone else if that matters) running
system 5 unix (no source of course, we have 4.2bsd source on a vax if that can
be modified). The box is of the opinion that its uuname is `clm' we would like
to convince it otherwise; there does not seem to be a hostname command, or any
equivalent. One system V that we have has a magic little file that lives in
/usr/lib/uucp that contains this name, does callan?
It seems to me that I read somewhere that the host name was compiled into
the kernel under sysV, that seems dumb, and unbelievable (we don't have source).
What am I missing?
George Williams
decvax!frog!aphasia!gww
There must be a better way.guy@sun.uucp (Guy Harris) (08/31/85)
> The box is of the opinion that its uuname is `clm' we would like to > convince it otherwise; there does not seem to be a hostname command, or any > equivalent. One system V that we have has a magic little file that lives in > /usr/lib/uucp that contains this name, does callan? > > It seems to me that I read somewhere that the host name was compiled > into the kernel under sysV, that seems dumb, and unbelievable (we don't > have source). It may or may not be dumb and unbelievable, but it is true. Given the environment that the USG/USDL UNIX releases were, until recently, targeted at (namely, AT&T sites who had source, and who ran big machines with a wide variety of possible hardware configurations, so you'd build a kernel specifically for that machine), it's not that dumb. The intent is that the distribution would come with a "generic" kernel, whose sole purpose was to run on just about any configuration long enough to build a kernel tailored for your configuration. At that time you'd assign a name to the system and build a kernel with that name built in. A company offering S5 on their machine could, if AT&T's binary licensing terms permit it (I don't know whether they do or not - they *should*, but that's no guarantee), offer the contents of "/usr/src/uts/<machine>/cf" as part of their distribution, along with pre-compiled object libraries for the kernel. That's sufficient to build a tailored kernel and to set the system name. This solution fails to some degree in the case of 4.xBSD, where you may build a kernel which isn't completely generic but which will run on several machines (using the autoconfiguration code), and fails miserably in the case of the small UNIX boxes where there are a limited number of possible hardware configurations and where you may not trust the end user to be able to configure a kernel. Some micro vendors have a command that'll either patch your /unix (or whatever it's called) or your running kernel or both to give the system a particular name. If any such micro vendors didn't do this, but instead kludged up all the user-mode programs which want the system name to get it out of a file, they didn't do a very good job. CCI originally did that until I got fed up and hacked the "uname" command to patch the kernel if you have it a name as an argument. If you want, you can patch it yourself using "adb" (or, if you're feeling ambitious, write a program to do it). The structure returned by a "uname" system call is called "utsname". Unless the vendor has monkeyed with it, it consists of 5 (or 4, for System III) 9-character strings; the strings are embedded in the structure, not pointed to by pointers in the structure. Starting at the location "utsname" (or "_utsname", as is likely on most systems), there will be 9 bytes which will probably be the system name. The next 9 bytes after it (starting at "utsname + 9") will definitely be the system name unless something is badly screwed up. Just patch those to the name you want - remember to include the terminating '\0' (if the first string isn't the current system name, don't patch it). Remember to make a copy of the kernel before doing this, and remember to reboot afterwards if you only patched it and not /dev/kmem. It may not be optimal, but it's a lot better than, say, V7, where you needed all the source to do a sysgen (many V7 vendors changed this, but out of the box you needed source) *and* the name of the system was not affected by a sysgen - it came out of an include file and was compiled directly into user-mode programs (many V7 vendors fixed this, also). Guy Harris
tim@cithep.UucP (Tim Smith ) (09/01/85)
Sounds like a job for adbman! Look at location utsname in /unix. There
you will find a string with the name of the machine ( actually, you will
find TWO strings with the name of the machine. I forget which one you
need to change. Better do them both ). Change these strings with adb.
I think they are eight character strings, null terminated iff less than
eight chars long.
--
unlk a6
rts
Tim Smith
ihnp4!{wlbr!callan,cithep}!timjww@sdcsvax.UUCP (Joel West) (09/01/85)
> Sounds like a job for adbman! Look at location utsname in /unix. There > you will find a string with the name of the machine ( actually, you will > find TWO strings with the name of the machine. I forget which one you > need to change. Better do them both ). Change these strings with adb. Actually, the 2nd is the uucp name. But not knowing who wrote what sloppy code, I wouldn't be brave enough to run a system with the 1st <> 2nd. Joel West CACI, Inc. - Federal (c/o UC San Diego) {ucbvax,decvax,ihnp4}!sdcsvax!jww jww@SDCSVAX.ARPA