Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs.

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Please explain the following o/p of “top” command

Please explain the following line from the "top" command in the bold :- Mem: 1026228k total, 449640k used, 576588k free, 44812k buffers Swap: 1052248k total, 2020k used, 1050228k ...
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345 views

Anacron and fcron, what are the differences?

Anacron is a computer program that performs periodic command scheduling which is traditionally done by cron, but without assuming that the system is running continuously. fcron is another ...
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1answer
151 views

Crazy idea: Identify if system is idle when it's a black box

I need to be able to tell if a series of servers have anyone active on them, and if not then to automatically shut them down (turn off the VM). It's not a trivial task, because I have 1000+ server ...
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5answers
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iptables vs. hardware firewall

I was wondering if anyone could speak to the advantages of a hardware-based firewall vs using iptables directly on a web server. I'm evaluating the cost effectiveness of having a dedicated firewall ...
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1answer
4k views

How do I set 'max threads per process' ulimit for non-root user?

Ulimit man page suggests -r option will set this but it only appears to be valid for the root user and there is no equivalent for setting it via /etc/security/limits? Any ideas?
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What will prevent a reboot?

I've got a Mac fileserver that isn't acting right (and was acting strangely yesterday as well). I set up an audible ping to it, and sshed into it and, as root, issued the reboot command. It did ...
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2answers
148 views

Trying to delete a directory stored on a Windows server, from on a Mac, containing files created on the Mac, getting “Directory not empty”

I am trying to delete a directory stored on a Windows 2008 R2 server, mounted on a Mac as network home (10.8.5). The directory was created by Safari and stores temporary internet files. I need to be ...
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5answers
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Groups and Permissions: Nested UNIX groups

We are getting more and more outside developers (from different clients) and are beginning to need a better strategy than adhoc adding to our server and adding to them ourcompany group (which owns ...
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8answers
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Bash snippet to move all files in a directory into that directory

I have a directory with lots of files and directories in it. In order to tidy it up, I'm going to put all those files into a directory, so I was going to do something like this: $ ls | wc -l 123 $ ...
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5answers
3k views

What are the benefits of the Logical Volume Manager

What are the features and potential benefits of Logical Volume Manager beyond what is detailed on its Wikipedia page?
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4answers
2k views

Combine multiple unix commands into one output

I need to search our mail logs for a specific e-mail address. We keep a current file named maillog as well as a week's worth of .bz2 files in the same folder. Currently, I'm running the following ...
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9answers
370 views

Can my operating system be a VM?

This isn't a server question per se, but I wonder if I can have my operating system be, more or less, a VM. Right now, I have Windows XP, and run linux (most of the time) in VMware. I would just ...
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841 views

How do I scp to a user I don't have the password for?

Here is the situation. I have user access to a server and root access to the same server. I want to edit files for a user that I don't have password information for on the server. ssh'ing as root is ...
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5answers
1k views

Linux command equivalents in opensolaris (and vice versa)?

So we just recently moved to a host that is based on opensolaris rather than a variant of linux. I've found that there are a bunch of commands that don't operate the way I'm used to on linux ...
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5answers
518 views

Restore old SunOS tapes

I have some old SunOS tapes I need to look at the table of contents before I shred them. Is there a Linux solution to restore these tapes?
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8answers
1k views

Tools for Monitoring Multiple Unix Based Systems [closed]

What's your suggested tool to monitor multiple Unix (Linux and OSX specifically) based systems at the same time? I need to monitor the utilization of the CPU, memory, and disks in real time and would ...
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2answers
7k views

Getting the last match in a file using grep

What's the best way of getting only the final match of a regular expression in a file using grep? Also, is it possible to begin grepping from the end of the file instead of the beginning and stop ...
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5answers
3k views

How to translate error number to 'errno' constant?

Suppose I have an application running on a UNIX box that is failing with a system error status of '13'. Now, I can easily look up this value in errno.h, to find out that it is a permission-denied ...
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1k views

How to create union of two directories?

In case of unix/linux, is there a way to create union of two directories without copying or linking manually everything to a single directory?
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3answers
868 views

Faking the date for a specific shell session

I'm certainly trying to achieve something weird here, but I want to fake the date locally for a shell session on GNU/Linux. I need to black-box test how a program behaves at different dates, and ...
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5answers
3k views

How to include all files from a directory in shell script (/etc/init.d/iptables in this case)

I have an /etc/init.d/iptables start|stop|restart script on different ubuntu servers (which is a normal shell script) For each new service I have to edit and insert a line to open a port. This leads ...
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2answers
1k views

Why does chmod(1) on the group affect the ACL mask?

I am trying to understand this Unix behavior (which I happen to be testing on Ubuntu 11.10): $ touch foo $ setfacl -m u:nobody:rwx foo $ getfacl foo # file: foo # owner: michael # group: michael ...
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3answers
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Why doesn't “ifconfig” work on some of my machines?

Some do...some don't work. ifconfig -bash: ifconfig: command not found
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5answers
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Unable to remove file using 'rm'

In one of our severs (IBM AIX), we have a file in path /data/1002/ which we were not able to remove or delete using the 'rm' command. The error message we got is "rm: S1208001.002: A file or directory ...
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100 views

Putting server configurations in version control via SSH

I have a bunch of *nix servers in production. I would like to put it's important configuration files in version control The basic idea I had was to Put a distributted version control system so ...
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5answers
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Command line SIP dialer

Is there a simple command line SIP dialer for unix which can connect to SIP server, make a call and play some media file (wav/mp3)? In ideal I would look like this: sip-dailer +1xxxxxxxxxx ...
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Why are files being removed from /tmp?

I use centOS5, but these files of /tmp is deleted automatically when time passes. What kind of structure will this kill him in? In addition, How to stop this?
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Java default JRE parameters on Unix

Is it possible to configure java in unix to always add a JRE parameter whenever java is run? e.g. -Dcom.sun.management.jmxremote.port=25800
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Skip over intermediate server via SSH

I just got hired to work in a lab with a big 'ol linux cluster. I'm a mac/windows guy, so I'm still trying to figure out how to navigate around using a 'nix command line. So far I haven't run into any ...
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How to check what port mysql is running on

On my windows dev box mysql is running on port 3306 How can I check what port it is running on the unix server that I have to upload the app to.
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182 views

Store system passwords with easy and secure access

I'm having to handle several VPS/services and I always set passwords to be different and random. What kind of storage do you suggest to keep these passwords safe and let me access them easily? ...
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2answers
173 views

What's a good way to supply a password for automating a backup?

So I'm looking at this question: How do you backup your websites? I was creating a script to be used with cron, and then I realized I would have to somehow input the password in the script. What is a ...
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3answers
207 views

Is there any reason to store my data in /var/?

Right now I have a small server handling a few things—DNS, HTTP serving, email, etc—and am storing all my data in /data/, a directory I create on all servers I administrate. The reason I like to ...
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In unix, what's the best way to reduce the size of a massive log file that is actively being written to?

On a linux server, I want to reduce the size of a log file which is several GB big. Cutting off the top half, or maybe the first million lines would work.
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Is it a good idea to encrypt files in unix?

There are (pdf) files placed under unix with 700 permission. The files contain sensitive data. Would it be a good idea to also encrypt these files? Would it make them any more secure?
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Is there a way to grep with a constrained file type?

right now i am using something like this: find . -name "*.xml" | xargs grep -l "foobar" it works, but i was wondering if grep has this functionality built in?
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1answer
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How do I find circular symbolic links?

I'm working on a HP-UX system and I want to find if there are any circular symbolic links. So far I'm using the command: ls -lrt `find ./ -follow -type l` But it's only doing ls -lrt on current ...
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655 views

How can I create a Single-purpose keys (ssh) for use with scp?

I'm trying to setup a Single-purpose key for copying data to a remote server (using scp), but I'm not sure what the command="" on the key should look like in this case. Any ideas? Thanks!
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2answers
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execute su -c over ssh

I am trying to check the BIOS version of a server over SSH, a command that requires root privileges: ssh remote-server su -c dmidecode but this of course fails with the error: standard in must ...
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5answers
608 views

Basic Unix Commands

I am new to Linux and I am trying to create a cheat-sheet to help me remember common bash commands. If you know any of the commands for the tasks below, please post them. I appreciate it! Commands ...
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Does iowait include time waiting for network calls?

The proc(5) manpage describes iowait as "time waiting for IO to complete". This was mostly explained in an earlier question. My question is: while waiting in blocking IO, does this include waiting on ...
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3answers
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Enabling apt-get on a default Amazon EC2 instance which has yum installed

I'd like to call something like: sudo yum install apt to enable me to use apt-get as well as yum for installation. However this doesn't work. I get the following back: Loaded plugins: ...
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4answers
665 views

Single sign-on for a mixed-OS network

I am handling a mixed network of SCO Openserver, Slackware and Windows XP computers. Right now, the primary user accounts are kept on one SCO computer with usernames and passwords synchronized to the ...
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4answers
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Ganglia without multicast

I'm running Ganglia 3.1.2 on a network where there is no multicast (nor can I turn it on). Does anyone have an elegant solution for getting ganglia to work correctly? I found this: ...
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2answers
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How to find all ways in which a Unix user account is locked

I occasionally find myself in a situation where an undermaintained system has an account that's been locked out. The problem is that there are a variety of ways in which an account can be locked out, ...
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1answer
52 views

Discrepancy between size of database listed in Unix and Mysql

When I see the size of my db_1 its listed as only 4k. But when I show table status for db_1, I see that the total size is approximately 3.7 GB based on data length. Why is there this discrepancy? ...
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How can I test the security of my server?

How can I test the security of my server ? Please I know it is too general question. But I was wondering if there is a tester software or web service checking all ports of your server, or possibly ...
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Using a shell script to check if rsync made any changes

I've got a bash script that rsync's two directories. Sometimes there's a change, odds are there's nothing. I want to run a command only if rsync actually made a change (add/update a file). ...
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Linux: What are the possible values returned by `uname -m` and `uname -p`?

I know that, for 32-bit Intel Linuces, it returns i[3-6]86. For 64-bit Intel, it says x86_64. But what about other, exotic architectures? (PowerPC, Alpha, SPARC...) Is there an authoritative list ...
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What's a proper way of checking if a PID is running?

I have a .pid file, and I need to check if the process is running. So far I found two options kill -0 `cat something.pid` which prints out an error if the pid isn't running. I know this can be ...