Ask MetaFilter questions tagged with Unix

Possibly the most specific -filter in recent memory

The Lurkers Support Me in Email — Mon, 14 Dec 2009 16:14:58 -0800

GUIDPartitionTableFilter: How can I non-destructively change a partition's filesystem type ID in OS X? For some reason (which I'll add at the end so I can get to the point) a partition on my external USB drive is mistakenly flagged as 'Microsoft Basic Data' and not 'Apple_HFS', as shown by diskutil:

$ diskutil list

/dev/disk0

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *500.1 GB   disk0

   1:                        EFI                         209.7 MB   disk0s1

   2:                  Apple_HFS Macintosh HD            402.5 GB   disk0s2

   3:       Microsoft Basic Data Boot Camp               97.1 GB    disk0s3

/dev/disk3


   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *1.0 TB     disk3

   1:                        EFI                         209.7 MB   disk3s1

   2:       Microsoft Basic Data                         999.9 GB   disk3s2

            ^^^^^^^^^^^^^^^^^^^^ Wrong!

When I plug the disk in or boot up, Snow Leopard complains about not being able to recognize the disk and asking if I want to initialize it. However, if I do mount_hfs /dev/disk3s2 /Volumes/Test the drive is mounted and I can access the filesystem just fine.

How can I change the type back to Apple_HFS? I've looked at the gpt and diskutil man pages but only found info pertaining to creating new partitions, not modifying existing ones.

OS X: How to track down and kill a cron job. Or something.

al_fresco — Sat, 14 Nov 2009 15:09:39 -0800

OS X Unix filter: Please help me find and delete an obsolete cron job on an iMac running Leopard. I'm doing tech support for a small office. A previous provider setup a cron job or something to create an rsync backup to a MacMini server every day at the same time. The backup configuration has changed, but this one job keeps trying to run. I can't find the script to delete it and am getting a bit frustrated.

I've tried

crontab -e - which shows an empty crontab.

I've looked in StartupItems, looked in /usr/bin/, usr/sbin/ for a compiled script, looked in the logs to see if I could see the source of the job, but it doesn't log to system.log or console.log. I did find the log that was set up for the backup, but it doesn't say the path of the original script. I know it's running because it was set up to also send an email to the office administrator. She gets a failure message daily.

I'm pretty sure it's not a LaunchDaemon, as the job was set up by someone who was using old-style tools, and all of the LaunchDaemons I could find were stock OS X.

Any idea how I can track this thing down and kill it for good?

Thanks!

Unix web apps

yegga — Tue, 10 Nov 2009 16:49:38 -0800

A two parter: 1. I remember reading a quote by someone along the lines of 'every new 'killer web app' is a unix app. google=grep; facebook=wall; etc. Can you help me find this please? 2. Now that you grok the idea, can you tell me more analogs of unix vs web apps? Which unix apps are yet to be made webby? Which have been, but badly implemented? Which are your favorite unix apps? Etc.

Quality Command Line Graphing?

DU — Tue, 29 Sep 2009 06:41:19 -0800

Open source, command line, low "impact", png-producing, full-featured, good-looking graphing on Linux and other Unices? We are using a script (Tcl, if it matters) to generate a script that will be sent in an email. Right now, we are using gnuplot. It's been a source of problems. No one particular thing, we just often have "issues" generating our graphs, many of them attributable to gnuplot weirdness. I'd like to rewrite it more robustly and eliminate gnuplot (on a three-strikes basis).

The "open source" and "command line" are pretty self explanatory. BTW, I don't really consider gnuplot to be command line, because it has its own shell. Yes, you can script it, but I'm looking for something that will take everything (except the actual data) as command line options.

"Low impact" means "not a lot of extra libs required" and is on the list because we have to manage, build and ship this stuff.

"full-featured" means that something that just draws a squiggle isn't enough. The particular graph we are sending out is actually a multiplot, i.e. two graphs in the same image file. We need to be able to label axes, change colors, set ranges, etc.

"png-producing" I think is non-negotiable. Personally, I would be happy to switch image formats (or better yet, go with SVG), but this email has to meet certain other requirements and I dasn't mess with the format.

"Other Unices" include Solaris and Irix. It doesn't have to ship with those OSes, though, as long as it will compile there painlessly.

As for "good-looking": Plotutils is actually perfect, except for one problem: The font rendering (actually, rasterizing) is complete ass. As in nearly unreadable even at reasonable sizes. I actually confirmed this with the maintainer that there is no way to make them look better at the present time.

How to centralize adminsitration of multiple Unix machines (and others)?

Imhotep is Invisible — Wed, 09 Sep 2009 11:45:34 -0800

I'm curious as to what are the current "best practices" when it comes to centralized administration of a network of Unix (primarily Linux, but not necessarily so) machines? Essentially, what is the equivalent of Active Directory for a network with one or more Unix hosts? The immediate answer I come up with would be something like OpenLDAP plus PAM but what I'm looking for is the suite of tools (GUI and CLI apps) for managing the directory, deploying software, centralizing sign-on and security, managing printers, etc. In a perfect world, I would like to centralize administration of Windows, Unix, and OS X machines via a single directory service, though I imagine such a solution would be expensive and/or cumbersome if it even existed. Or is this something Samba 4 will do?

Color laser printer with Linux/UNIX drivers available

noztran — Mon, 31 Aug 2009 07:23:08 -0800

Could anyone recommend a color laser printer for ca. 500 GBP for a small office? Compatibility with Linux and Solaris---essential. BONUS question: should I also buy a monochrome laser for B&W printouts or is an unnecessary overkill when one has a color laser?

Case-Insensitive LS on Mac OS X?

WCityMike — Sun, 16 Aug 2009 11:03:27 -0800

Unix mavens: is there a way for ls on a Mac OS X install to alphabetize its listing case-insensitively, while still preserving any other ls flags you may be using? If not, does another ls variant offered by anybody offer case-insensitivity, and if so, how can I supplant one with the other, without risk of any harm to anything else on my system? (If it matters, my shell of choice is tcsh.)

Attending a Seminar 101

Mach5 — Fri, 07 Aug 2009 13:38:22 -0800

I need to pick a seminar/conference/class/training/whatever for work to attend within the next 6 months or so, I have until 10PM to choose, and I have no idea where or what the cool stuff is. It should be at least tangentially related to my job as a Unix Systems Engineer/Python Guy, and preferably within the Northeast (NYC is where I'm located), although feel free to recommend anywhere in the US. I'm a django/python coder, but mainly a linux engineer. I'd like anything that is cool and interesting, a la DEFCON/HOPE/etc. It can be anything related to python, linux, AIX (ugh), solaris, high performance computing, clusters, networking, security, etc.

So, metafilter, what do ya got for me? Be forewarned that I fall asleep easily when I am bored, so I need something at least halfway interesting, that will also improve my skills.

Shell script handling CSV columns

fightoplankton — Wed, 10 Jun 2009 16:30:20 -0800

I'm using a shell script to handle some excel docs by converting to csv and reformatting it a little bit. I'm having some difficulty going on with the next part of the script. Some help would be great. :) CURRENT SCRIPT:
#!/bin/sh
ls *.xls
echo "Enter filename for excel input file: "
read filen
xls2csv -x "$filen"".xls" -b WINDOWS-1252 -c "$filen"".csv" -a UTF-8
sed '1,3d' "$filen".csv >"$filen"_temp.csv
cut -d "," -f 1,4- "$filen"_temp.csv > "$filen"_temp2.csv
awk -F, '{sub($NF, "");print}' "$filen"_temp2.csv > "$filen"_temp3.csv
sed 's/.$//' "$filen"_temp3.csv > "$filen"_fixed.csv
rm "$filen".csv
rm "$filen"_temp.csv
rm "$filen"_temp2.csv
rm "$filen"_temp3.csv
echo "$filen"".xls corrected and saved as ""$filen""_fixed.csv"

EXAMPLE OUTPUT (first three lines only):
"Device ID","1) S31 Which best describes how you answered the online reading comprehension quiz?","2) S32 Which best describes how you answered the online timed retrieval quiz?","3) B19. If you want your product to be easy to find in the supermarket then you should make its container","4) C19. So that he can shift attention between the radio and his incessantly talking girl friend when she is in the car, Joe adjusts his radio","5) B20. Early selection is most likely to occur for","6) C20. Early selection for a red target is most likely to occur when there is","7) B21. In a lexical decision task, when the target is a bird name, e.g. robin, it is usually preceded by the prime BODY but is sometimes preceded by the prime BIRD.","8) C21. In a lexical decision task, when the target is a dog name, e.g. collie, it is usually preceded by the prime CAR but is sometimes preceded by the prime DOG.","9) B23. Suppose that that you see a brief display with 12 colored letters: 4 red, 4 white, and 4 blue. At the offset of the display you hear tone. A tone instructs you to report only the letters of a particular color: high for red, medium for white, and low for blue. About how many letters do you report?","10) B22. Sperling (1960) found that partial report produced the highest estimate of the number of available letters when the tone occurred ","11) C23. According to the logic of Sperling’s (1960) partial report method, an observer who reports three letters from a row in a 4 x 4 display that was cued at the display’s offset must have seen at least","12) C22. Sperling (1960) found that the greatest difference between full and partial report in the number available of letters was when the tone occurred ____ milliseconds after the offset of the visual display"
96A39,6,4,"4 c","4 c","5 c","5 c","5 c","4 i","3 c","1 c","1 i","5 i"
1E90A4,5,3,"4 c","4 c","5 c","5 c","2 i","5 c","3 c","1 c","4 i","4 i"

First, I need to remove the numbering of the questions from the first line. So "1) S31 Which best describes how you answered the online reading comprehension quiz?" would become "S31 Which best describes how you answered the online reading comprehension quiz?"

Next I need to remove an entire column if its row header doesn't begin with either B or C or is the "Device ID" column. For example, column starting with B19 is kept, the C23 is kept, and"Device ID" column is kept. The column with the question starting S31 must be entirely removed.

Thanks.

What log file would show when a Mac OSX user was renamed?

neilkod — Thu, 04 Jun 2009 18:01:11 -0800

on Mac OSX Leopard(10.5.7), which log file, archived or not, would I find when a user account was renamed? Easy as that. A user account on a machine was renamed. I'd like to find out when. I'm currently logged in as the admin but do not have the admin password.

How to test if a variable in a Bourne shell script is an integer?

InsaneRhino — Thu, 30 Apr 2009 13:26:15 -0800

I'm being tasked with creating a simple integer calculator, which I have effectively done, up to the point of it being a calculator, however, even after hours of searching I cannot get any scripts to work correctly. Here is my code so far:

-----------------------------------------------
#!/bin/sh
echo "Please enter your first number"
read a
echo "What operation would you like to perform? (+,-,/,x)"
read orp
echo "Please enter your second number"
read b
echo $op
if [ $opr = "+" ]
then
op=`expr $a + $b`
echo "$op"
elif [ $opr = "-" ]
then
op=`expr $a - $b`
echo "$op"
elif [ $opr = "/" ]
then
op=`expr $a / $b`
echo "$op"
elif [ $opr = "X" ]
then
op=`expr $a \* $b`
echo "$op"
fi
-----------------------------------------------

Thanks for any assistance!

Help me administer Mac OSX Mail Server

rkent — Wed, 22 Apr 2009 13:18:40 -0800

Help me administer a mail server on OS X. Some friends and I have run a small web / database / email server for several years. Originally it was Linux, which I'm relatively familiar with; a while back we moved to OS X (Server) at the behest of one of the guys. Now for various reasons his availability for server admin duties is severely curtailed, and I'd like to pick up the slack rather than pestering him with questions.

Most pressing is the email server. I have no idea how to run it. I've tracked down pages like this, and I'll continue to search the Apple website, but any third-party FAQs or HOWTOs would be very appreciated. Even the really basic stuff, like: what is the name of the mail server process / executable(s), and where are their config files? What logs should I check when there are errors? Basically, help me approach the OSX server utilities with my Linux-based brain.

An additional level of difficulty is presented by the fact that I'll be doing any admin 100% at the command line; I don't have a Mac and so I lack the GUI server tools.

No reserved blocks in ext2 on Aspire One?

Busy Old Fool — Mon, 06 Apr 2009 20:32:42 -0800

Why is it OK to have no reserved blocks in ext2 on the Acer Aspire One? This guide to recovering space on the Acer Aspire One gives as one suggestion:
By default the ext2 filesystems reserves 5% of all blocks for the superuser. You can safely set this to 0% and gain additional 325MB, or 375MB if you also remove the swap partition.
sudo tune2fs -m0 /dev/sda1

Now, I think I understand what reserved blocks are and why. Basically, it's because to avoid a situation where the free disk space drops close to zero, root doesn't have room in /var to do even the most basic things and the whole system starts falling apart. Please correct me if that's wrong or incomplete.

So why is it OK to unreserve these blocks on the Aspire One? Is there something about the way Linpus is set up that makes the above scenario impossible?

UNIX PDP-11 Riddle Filter: help me outsmart my computery friend...

lalalana — Sun, 05 Apr 2009 20:06:46 -0800

UNIX PDP-11 Riddle Filter: help me outsmart my much-beloved but smug computery friend... he's giving me the business, and thinks I can't figure out the following statement:

if a hacker at MIT running UNIX on a PDP-11 were looking at the time
when i was born, it would look like this:

336451500

Obviously, I can't. I don't even know how to google to begin to figure out the answer! I tried! But, I do know how to harness the power of collective intelligence. So, what time was he born? And, also, since I'm no slouch, I'd love to learn how I'd figure out such a thing if I ever had to again in the future...

Joining MP3 Files Together Based on Date in Filename?

WCityMike — Wed, 25 Mar 2009 16:08:55 -0800

I have a podcast that downloads as multiple segments over multiple days. Its format arrives as YYYYMMDD_showcode_segment.mp3; so, for example, one download might result in files as 20090323_goofa_01.mp3 through 20090323_goofa_21.mp3, and also within the same download 20090324_goofa_01.mp3 through 20090324_goofa_21.mp3. What I'm looking for is a Unix script (shell, perl, what have you) that would look at a directory and look at what dates are represented there, and let me join all of the segments together by day. I can use mpgtx -j to do the actual joining; I'm looking for the code that would let the script determine what dates are in the directory and then get each day's segments united into a single MP3 for that day's show.

Granular volume data from MP3 files?

joe vrrr — Tue, 10 Mar 2009 10:13:54 -0800

I'm looking for a command-line tool that can return a volume value for specific points of time in an MP3 file. Basically, I need an array of volume values for an MP3 file. Preferably, one value for every 1/30th of a second of audio. The data will be used for visualization, so the values don't have to be extremely accurate or in any particular unit of measurement.

In a perfect world, this would be an open source python-based tool.

Any ideas?

Hardware question about installing *BSD on old Sun equipment as a SOHO firewall/router.

Myles — Sun, 01 Feb 2009 11:25:51 -0800

Can someone give me any pointers, tips, or caveats about installing BSD on sun hardware for use as a firewall/router? I've been pondering a while about installing OpenBSD on an old Sun Netra T1. I plan to use it as a firewall/router using pf and maybe squid and Proxy on it. I used to have an old Netra X1 with no CDROM drive, and while memory escapes me, I don't think I had much luck trying to get a different OS on there, as I couldn't even get to the OK prompt, ultimately resorting to "jumper tricks" suggested by some folks. I suppose I'm just doing it for the hell of it, and I know I'm going out of my way for an unorthodox use of a Sun machine, but its really something that's tickled my fancy for a while.

For those who have worked with Sun hardware, what are those config cards for? Any tips or caveats when doing this kind of project? I still plan to have a wireless router that'll merely serve as a wireless ap. I think I can just hang that off a switch.

I've thought about getting something from Soekris Engineering or PC Engines, but last time I looked, getting a used Sun machine on ebay is actually cheaper, so I don't wanna spend too much. :) The Sun Netra PSU is loud though.

WE HAVE COMPUTERS

djgh — Wed, 26 Nov 2008 16:57:38 -0800

Found an old computer in the basement. What steps should I go through to get it up and running? Seems a previous tenant left a computer tower in the basement. It's from, at the newest, 2003.

I plugged it into power, hit the on button, and stuff whirred, and green lights came on. It doesn't have any cables, mouse or a monitor, and my access to a monitor will be limited to what I can borrow off friends for short periods (have a MacBook, if there's some neat trick to be able to use it as a monitor...).

What can I do to get this up and running (thinking of installing Linux or BSD) - what bits will I need to scrounge, what should I do to check that everything's in place hardware-wise etc.?

And secondly, what flavour of Linux/Unix should I install, and how can I go about making this thing useful beyond being a pretty neat geeky playground?

Basically, what's the ABC of going from pile of junk to functional in this situation?

vi / vim editor: Can I paste text inside a colon command?

alb — Tue, 21 Oct 2008 12:19:35 -0800

vi / vim editor: Can I paste text inside a colon command? (Long-time emacs user here, having a great time learning vim) I often want to copy some text and then use it as the match portion of a substitution command, rather than re-typing it. I've looked over the FAQs, the tips, etc. and didn't see this addressed. Is it possible? Or is there some other vi-specific idiom for doing the same thing?

Bonus question: As I'm still getting my head around the vim terminology and resources, what/where could I have searched to find this answer myself?

How do I tell my Mac that I'm me?

grumblebee — Wed, 15 Oct 2008 07:17:27 -0800

Question about changing my terminal prompt (and other matters) in an OS X Bash shell. I'm not the most experienced Unix guy, but I can usually figure things out. But this one has me stumped: I just got a slightly-used Macbook Pro. The previous ower -- Michael -- gave me his admin password. So I went into System Preferences, Accounts and created a new admin, grumblebee. Then I deleted Michael.

All went well until I opened terminal, where I saw that the prompt looked like this:

michaels-mackbook-pro: ~Grumblebee

(I know that ~Grumblebee isn't part of the prompt. I just wanted to show you that I'm logged in as me and it's finding my home directory. It's just the prompt that's wrong.)

I tried to edit etc/baschrc, but it said I didn't have permission.

How can I change the prompt and is it likely I'll encounter any other problems connected to changing users?

Restricting access to a symbolically-linked path using htaccess

jpoulos — Tue, 14 Oct 2008 07:13:25 -0800

Can I restrict access to a symbolically-linked path using htaccess? I have a Solaris file system that my Apache web server accesses through a symbolic link. I need to restrict access to those files to a select group of users. The rules for access are in a MySQL db, so I'm thinking I can run a cron to regularly generate an htpasswd file. An htaccess file won't work on the remote file system (which isn't running apache), though, will it? Can I add something to my httpd.conf file which will make users authenticate before accessing content on the other side of that symlink?

What is the linux command 'dt'?

logicpunk — Mon, 06 Oct 2008 10:05:17 -0800

Obscure linux/unix text processing command: what is 'dt'? I'm trying to figure out what one of my boss's data analysis scripts is doing, and I'm hung up on this weird little command called dt. There aren't any man or help pages for it, and googling around hasn't come up with anything.

The script I'm looking at reads in a formatted data file ('tmp') with X numbers of columns. Each row is a consecutive point in time. The line I'm stuck on reads as follows:

cat tmp | dt t 1 t 2 t 3 d 12

The numbers specify columns, but I'm not entirely sure what the 't' and 'd' arguments are doing there. I suspect the script is sorting the data in some fashion, and I could figure it out eventually (or, god forbid, ask the boss), but I'd like to know what the command is and where I can find more information about it.

How can I grant user access to one directory only, so they can edit a file?

media_itoku — Fri, 03 Oct 2008 12:02:20 -0800

How can I grant user access to one directory only, so they can edit a file? I'm sure there's a way to do this. I'm hosting a site and I want to allow a person access to one directory, so that he can edit the php file in it whenever he wants. What's the best way to do this?

It seems to me that my options are: 1) set up a new user in my hosting and give him FTP access to the folder (I'm on Dreamhost - not sure how to do it, or how to stop him from seeing the entire domain). Problem with this is that then I won't own the files, right?
2) There might be some kind of user management system that can a) let the person log in. b) Give them a web front-end with an editor so they can edit the file. I've looked at hotscripts.com but they don't seem to be quite what I want.

Unfortunately I can't put the script in a database in joomla etc because it is feeding information to a shockwave application. So it needs to be a separate file. Which I think rules out number 2. Am I missing something?

Per VHost Apache Bandwidth Stats

Brian Puccio — Tue, 16 Sep 2008 06:56:14 -0800

Linux/Unix Admin Filter: What is your preferred method for monitoring bandwidth use per virtual host in Apache? I could just log everything and run AWStats/Webalizer/whatever, but that seems overkill when all I really want is a MRTG or RRD Tool graph for each virtual host to indicate bandwidth used the last day, week, month and year. Do you use the impossible to find mod_watch or something else?

Just need a folder of my own, that's all!

dance — Tue, 02 Sep 2008 05:04:10 -0800

Would anyone care to comment on the most practical way, given access to a command line Fedora box, I can obtain a copy of a folder and its contents? The box is connected to the net but I don't know enough Unix to, for example, get a tar of the folder and have the machine email me a copy. Although thinking about it, the folder is probably just a little too big for that. I have SSH and physical access but FTP isn't working, which is the whole problem in a nutshell, really. If anyone is interested in 10 minutes' brainstorming feel free to mefi mail me!