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Old 05-10-2006, 09:47 PM   #31
OldSeaDog
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man ln (as a general rule I use info instead of man - info pages are easier to digest when they do exist, and if they don't you should get the man page anyway), assuming the package is installed, and ln certainly will be.
 
Old 05-10-2006, 09:52 PM   #32
OldSeaDog
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chrisdm mentioned RedHat being free from the company (I assume he meant by download from the website). The only distro I am aware of that is free from the company (i.e., they ship you the CD's free of charge) is Ubuntu, who will even ship you several if you have a use for them, and THEY pay the freight, anywhere in the world. Now that is awesome!
 
Old 05-10-2006, 10:45 PM   #33
chrism01
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Actually, I was just trying to distingish between distros (ie SW) and companies eg RedHat effectively has 2 distros:
1. Fedora Core - totally free and bleeding edge
2. Enterprise Linux series - have to buy from RH, not bleeding edge (NB you can get a free ver of this from eg Centos)
For other distros, ask someone who has dealt with them eg the qn of incorporating media player SW or not arises.
 
Old 05-11-2006, 12:03 AM   #34
Simon Bridge
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Sometimes data is stored bitwise in a file, but the physical memory is organised in terms of whole bytes. (cpu instructions, for eg, are bytes, words or longwords, the program counter ticks off whole bytes at a minimum etc. Of course, this is the hardware level.) One accesses individual bits with shift operations. Thus, I'm not sure this is actually an "error" - at least not the same as 0xFF=256 is an error.

Nice try though and a good point.
 
Old 05-15-2006, 05:19 AM   #35
JZL240I-U
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Quote:
Originally Posted by Simon Bridge
Are you saying there is a file called "grub" in the /boot/grub directory, which is a link to /boot/grub ?

Show us - cd into that directory and post the output of ls -l (show us the link).

[...a lot of coherent text ...]

I hope this is coherent.
Here goes, though it is the /boot directory, not /boot/grub as I wrote first:
Code:
/boot> ls -l
...
boot -> .
...

/boot> cd boot
/boot/boot> pwd
/boot/boot

/boot>boot> cd boot
/boot/boot/boot> 
{as often as you want to, btw....}
/boot/boot/boot> pwd
/boot/boot/boot

cd grub
/boot/boot/boot/grub> 
/boot/boot/boot/grub> pwd
/boot/boot/boot/grub
So it is "infinite" but what for?
 
Old 05-15-2006, 08:08 PM   #36
Simon Bridge
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hmmm none of that looks like the output of ls -l... compare with this:
Code:
$ ls -l /boot
total 17893
-rw-r--r-- 1 root root  238016 2005-10-11 02:18 abi-2.6.12-9-686
-rw-r--r-- 1 root root  261843 2006-04-05 10:02 abi-2.6.15-20-686
-rw-r--r-- 1 root root   63599 2005-10-11 01:23 config-2.6.12-9-686
-rw-r--r-- 1 root root   69294 2006-04-05 06:30 config-2.6.15-20-686
drwxr-xr-x 2 root root    1024 2006-05-06 01:08 grub
[snip]
... spot the diifference? Soft-links looks like this
Code:
$ ls -l /dev/modem
lrwxrwxrwx 1 root root 10 2006-05-16 11:45 /dev/modem -> /dev/ttyS0
...

Notice that I include the command and the entire output? This makes everything clear as if you were sitting in front of my machine issuing the commands.

Now I take it you just included the last part of each line?

It appears that in the /boot directory, you have a file called "boot" which is a link to "." - so cd boot is the same as cd .

Here's what I think you are showing me:
Code:
$ ls
custom   downloads      DSL-stats.txt~  music  photos    simon
Desktop  DSL-stats.txt  games           phone  projects  vultures
simon@indigo-prime:~$ ls -l simon
lrwxrwxrwx 1 root root 1 2006-05-16 11:51 simon -> .
simon@indigo-prime:~$ cd simon
simon@indigo-prime:~/simon$ ls
custom   downloads      DSL-stats.txt~  music  photos    simon
Desktop  DSL-stats.txt  games           phone  projects  vultures
simon@indigo-prime:~/simon$ cd simon
simon@indigo-prime:~/simon/simon$ ..
simon@indigo-prime:~/simon$
See?

I made a symbolic link in my home directory pointing to the dot.
The path in my prompt just records the path that I took to get there, not my location in the file system. (It's the difference between saying "go north one mile, east one, then south one" instead of saying "go east one mile". The first is what the prompt is recording, the second is where you ended up.)

The only reason for needing a link like that is if some program executed in the /boot directory referrs to "boot" when it needs to refer to "." ... this can happen if the program writers expected it to be someplace else. (Imagine a script intended for the root directory which has the command "cd boot". In the root directory, this will work. But the distro maintainers decide the script is more appropriate in the /boot directory to start with. Rather than hunt through and change every reference to "boot", it is often simpler and quicker just to add a symlink. This is a simple example, this workaround is normally used in much more complex situations - and normally only temporarily.)

Generally - circular links are Bad and should not be used. I have none in /boot, for eg.

Last edited by Simon Bridge; 05-15-2006 at 08:11 PM.
 
Old 05-17-2006, 08:36 AM   #37
JZL240I-U
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Quote:
Originally Posted by Simon Bridge
hmmm none of that looks like the output of ls -l ... compare with this ... spot the diifference? Soft-links looks like this ...

Notice that I include the command and the entire output? This makes everything clear as if you were sitting in front of my machine issuing the commands.
Okay, here it comes:
Code:
linux:/boot # ls -l
total 6056
drwxr-xr-x   4 root root    1024 Nov 12  2005 .
drwxr-xr-x  28 root root    4096 May 15 23:14 ..
-rw-r--r--   1 root root  756397 Sep 13  2005 System.map-2.6.13-15-default
-rw-------   1 root root     512 Nov 11  2005 backup_mbr
lrwxrwxrwx   1 root root       1 Nov 11  2005 boot -> .
-rw-r--r--   1 root root   63888 Sep 13  2005 config-2.6.13-15-default
drwxr-xr-x   2 root root    1024 Nov 26 18:12 grub
lrwxrwxrwx   1 root root      24 Nov 11  2005 initrd -> initrd-2.6.13-15-default
-rw-r--r--   1 root root 1741036 Nov 11  2005 initrd-2.6.13-15-default
drwx------   2 root root   12288 Nov 11  2005 lost+found
-rw-r--r--   1 root root  133120 Nov 12  2005 message
-rw-r--r--   1 root root   73508 Sep 13  2005 symvers-2.6.13-15-i386-default.gz
-rw-r--r--   1 root root 1838899 Sep 13  2005 vmlinux-2.6.13-15-default.gz
lrwxrwxrwx   1 root root      25 Nov 11  2005 vmlinuz -> vmlinuz-2.6.13-15-default
-rw-r--r--   1 root root 1541719 Sep 13  2005 vmlinuz-2.6.13-15-default
linux:/boot # cd boot
linux:/boot/boot # pwd
/boot/boot
linux:/boot/boot # cd boot
linux:/boot/boot/boot # pwd
/boot/boot/boot
linux:/boot/boot/boot # cd boot
linux:/boot/boot/boot/boot # pwd
/boot/boot/boot/boot
linux:/boot/boot/boot/boot # ll
total 6056
drwxr-xr-x   4 root root    1024 Nov 12  2005 .
drwxr-xr-x  28 root root    4096 May 15 23:14 ..
-rw-r--r--   1 root root  756397 Sep 13  2005 System.map-2.6.13-15-default
-rw-------   1 root root     512 Nov 11  2005 backup_mbr
lrwxrwxrwx   1 root root       1 Nov 11  2005 boot -> .
-rw-r--r--   1 root root   63888 Sep 13  2005 config-2.6.13-15-default
drwxr-xr-x   2 root root    1024 Nov 26 18:12 grub
lrwxrwxrwx   1 root root      24 Nov 11  2005 initrd -> initrd-2.6.13-15-default
-rw-r--r--   1 root root 1741036 Nov 11  2005 initrd-2.6.13-15-default
drwx------   2 root root   12288 Nov 11  2005 lost+found
-rw-r--r--   1 root root  133120 Nov 12  2005 message
-rw-r--r--   1 root root   73508 Sep 13  2005 symvers-2.6.13-15-i386-default.gz
-rw-r--r--   1 root root 1838899 Sep 13  2005 vmlinux-2.6.13-15-default.gz
lrwxrwxrwx   1 root root      25 Nov 11  2005 vmlinuz -> vmlinuz-2.6.13-15-default
-rw-r--r--   1 root root 1541719 Sep 13  2005 vmlinuz-2.6.13-15-default
linux:/boot/boot/boot/boot #
Some are colored, but I omitted that...

Quote:
Originally Posted by Simon Bridge
Now I take it you just included the last part of each line?
No, I re-typed that by hand, I had just jotted down the essentials by hand. The unabridged output above is a screen copy on a floppy...

Quote:
Originally Posted by Simon Bridge
... The path in my prompt just records the path that I took to get there, not my location in the file system. (It's the difference between saying "go north one mile, east one, then south one" instead of saying "go east one mile". The first is what the prompt is recording, the second is where you ended up.)
I see that you know maps . But I'm not sure you are right, that's why I did the repeated
Code:
pwd
and the outputs of "print working directory" shows the same location as the promopt does, so...

Quote:
Originally Posted by Simon Bridge
The only reason for needing a link like that is if some program executed in the /boot directory referrs to "boot" when it needs to refer to "." ... this can happen if the program writers expected it to be someplace else. (Imagine a script intended for the root directory which has the command "cd boot". In the root directory, this will work. But the distro maintainers decide the script is more appropriate in the /boot directory to start with. Rather than hunt through and change every reference to "boot", it is often simpler and quicker just to add a symlink. This is a simple example, this workaround is normally used in much more complex situations - and normally only temporarily.)

Generally - circular links are Bad and should not be used. I have none in /boot, for eg.
Thank you for the lucid explanations all over the thread (and particular why SuSE did their boot -> . thingy), supported by easily understandable examples.

You are of the kind of members who make this site so attractive -- learning on LQ is just great .

Last edited by JZL240I-U; 05-17-2006 at 08:39 AM.
 
Old 05-17-2006, 09:08 AM   #38
billymayday
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Cool

I hate to be a pedantic prat, but since I'm sitting here updating various packages I have nothing better to do, but
Quote:
"go north one mile, east one, then south one" instead of saying "go east one mile"
doesn't usually give the same result because of the curvature of the Earth.

As I said, I'm being a prat, but it's been a b$^%*y long week and day and I'm in one of those stupid moods we all get occasionally (I hope I'm not alone anyway).

Rgds and no offence intended

ps Simon - go the 'tahs in the Super 14

Last edited by billymayday; 05-17-2006 at 09:14 AM.
 
Old 05-17-2006, 09:18 AM   #39
Nylex
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Quote:
Originally Posted by billymayday
doesn't usually give the same result because of the curvature of the Earth.
I know this is OT, but I'm gonna reply anyway. The Earth's curvature won't make a difference to one mile, as it's a tiny fraction of the radius of curvature. Euclidean geometry (i.e. the kinda stuff you're used to.. angles in a triangle add up to 180 degrees, etc) still holds on the small scale.

Edit: oops, I wrote Eulerian when I meant Euclidean.

Last edited by Nylex; 05-17-2006 at 09:26 AM.
 
Old 05-18-2006, 07:06 AM   #40
Simon Bridge
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Quote:
Originally Posted by Nylex
The Earth's curvature won't make a difference to one mile, as it's a tiny fraction of the radius of curvature.
However, I note there are two places on Earth where those instructions would leave you where you started

This is not entirely off-topic, since both are home to penguins. Sort of.

Of course: the implication is that I'm talking about "walking" so we get uncertainties of the order of 30-50cm (pacing out a mile), and JZL240I-U (who I was talking to) is in Germany. I figure the resulting discrepancy due to the curvature of the Earth anywhere in Germany will be less than 60cm (or two uncertainties) allowing the example to be true to within 95% limits.

(This is the sort of problem I set physics students - the reasoning is more important than the answer.)

Quote:
Originally Posted by billymayday
As I said, I'm being a prat, but it's been a b$^%*y long week and day and I'm in one of those stupid moods we all get occasionally
You cannot get away from it: even space-time is non-euclidean. Now: just how bad a day did you want to have?

Last edited by Simon Bridge; 05-18-2006 at 07:13 AM. Reason: fixed bv code
 
Old 05-18-2006, 08:19 AM   #41
JZL240I-U
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Quote:
Originally Posted by Simon Bridge
However, I note there are two places on Earth where those instructions would leave you where you started

This is not entirely off-topic, since both are home to penguins. Sort of.
Hm. Can't be the poles, as there are no penguins at the north pole ... I can only think of one line 1/2 mile south of the equator for your instructions to work with the precision "required" by billymayday, the second eludes me and there are not so many special places on a rotating ellipsoid. So would you mind pointing to a solution?

Quote:
Originally Posted by Simon Bridge
Of course: the implication is that I'm talking about "walking" so we get uncertainties of the order of 30-50cm (pacing out a mile),
Then you have an impressively even lenght of pace. In my experience this error is exceeded already after 100 yards.

Quote:
Originally Posted by Simon Bridge
I figure the resulting discrepancy due to the curvature of the Earth anywhere in Germany will be less than 60cm (or two uncertainties) allowing the example to be true to within 95% limits.
One could calculate that but I'm quite sure it is much less than 60 cm due to the ratio (earth's radius ~4.000 miles) / (1 mile)

Quote:
Originally Posted by Simon Bridge
You cannot get away from it: even space-time is non-euclidean. Now: just how bad a day did you want to have?
Well, due to the differences between earth's surface and the geoid the curvature of space will prevent a true fit anyhow...


Umm, after this slight digress, how then did you explain the result of "pwd"
 
Old 05-18-2006, 08:43 AM   #42
Michael_aust
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i was under the impression having write permission to a diectopry allows you to write to the directory, but files within can have there own perminssion.
 
Old 05-18-2006, 10:02 PM   #43
Simon Bridge
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Michael_aust: you can check this easily.

Directories do not usually have write permission. Read permission is needed to see it and execute needed to see inside it. You need write permission in the directory to:

1. delete the directory
2. paste/create files into the directory, or move/remove them from it

... of course, contained files and sub-directories may have their own permissions. And I am prepared to be proved wrong if you want to provide an example?

Quote:
Hm. Can't be the poles, as there are no penguins at the north pole ... I can only think of one line 1/2 mile south of the equator for your instructions to work with the precision "required" by billymayday, the second eludes me and there are not so many special places on a rotating ellipsoid. So would you mind pointing to a solution?
Oh dear oh dear oh dear.

If you allow that "France" is a place, you will allow that "Antarctica" is also a place. There are penguins in antarctica - though not at the South Pole, admittedly. Start at the South Pole. (Actually, you cannot use a compass here - gps must be interesting.)

Of course - pedantically, the spot must be an equal distance from every point on the equator, and in the southern hemisphere... which makes this the rotational pole, and not the magnetic pole. In terms of rotation, this is a "north" pole. Annoying isn't it?

You can also start anywhere on a circle about 2km from the north pole (south-rotating pole). Oh - you cannot use a compass there either. But go north from anywhere on that circle and the next instruction will take you right around the pole.

(... and penguins have been released into the arctic as early as 1935. I understand the national zoo in Norway has penguins in captivity. Also the Awk is sometimes called the "arctic penguin".) http://dict.die.net/arctic%20penguin/

A half-mile south of the equator?? You would surely end up on the same parralell, but a mile from where you started. It would, indeed, satisfy the conditions of the first remark.

Penguins FYE: http://www.extremeimages.com/

Last edited by Simon Bridge; 05-18-2006 at 10:25 PM.
 
Old 05-19-2006, 03:59 AM   #44
billymayday
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Nylex, it's not so much from the non-euclidean front that I approached this (although I did take this in pure maths at university), but more from the fact that the poles are fixed points on a sphere, and as Simon points out, the closer to the pole you are, the greater the error.

On penguins in the Arctic, of course they are there. It's just that no one ever sees them as they have learnt to live in ice tunnels to avoid being eaten by Santa's elves
 
Old 05-19-2006, 04:16 AM   #45
teebones
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Quote:
Originally Posted by butters88
Hey everyone, I'm really new to Linux and I just had a few really basic general questions to ask. I'm sorry if these questions are answered somewhere else but I couldn't find them. If you could point me to a good site for these sorts of questions then I'd appreciate that too.

1) What is a regular file on a Linux system? What sorts of regular files can exist and what values can the bytes within each have?
ELF binary file (the counterpart of the windows .dll) | second part of the question i don't follow.

Quote:
Originally Posted by butters88
2) On Windows, most of the time when you install an application all its relevant files go in the same directory (ie. under Program Files\whatever), how is this different in Linux?
Many programs will install in /usr/local/whatever, however mostly this is only for the executables of the program, as the manpages and libs etc are installed in other directories.
(it depends on the app really)

Quote:
Originally Posted by butters88
3) In addition to the normal permission bits of a node (rwxrwxrwx) what is the 10th bit for and how is it special? What uses does the special bit have?
check this: http://www.faqs.org/faqs/hp/hpux-faq/section-70.html for deep detailed answer.

Quote:
Originally Posted by butters88
4) What does having write access allow you to do compared with write access on individual files? Does it give you write permissions on all files within? Or just the permissions to create new files?
Strickly speaking it only applies for the directory you set it on. The files inside maybe be able to be written within, depending on wich write permission you've set (user/group/anyone) and who owns the files.

Quote:
Originally Posted by butters88
5) What is an inode? What does it do? Are all the blocks which comprise an inode necessarily in the same physical location?
check : http://en.wikipedia.org/wiki/Inode for the answer.

Quote:
Originally Posted by butters88
6) Is it possible to hardlink directories in Linux? Why/why not?
yes this is possible, because you can

Quote:
Originally Posted by butters88
Thanks in advance, I know these are really stupid/simple questions, and I appreciate any answers you can give.
cheers.
 
  


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