From a unix admin standpoint what is the difference please between those terminologies : Service, Process, Thread, Task, Job, Daemon ?
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I know that an application is a program that you interact with on the desktop, but what exactly are processes and services?  Are services classified as processes or is it the other way round?
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In Windows 7's task manager, I can select different columns to show. There are a bunch that are related to memory and memory usage, but I'm not sure what it all means.  I have a Dutch installation of Windows, so I'll try to translate them; as I'm not sure of the English names.    In order:   Working set Peak working set Private working set Commit charge Paged pool Not-paged pool
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Linux doesn't actually distinguish between processes and threads, and implements both as a data structure task_struct.  So what does Linux provide to some programs for them to tell threads of a process  from its child processes? For example,   Thanks.
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System crontab:  /etc/crontab   Root crontab:  sudo crontab -u root -e   Which way is preferred? As they all run tasks within administration privilege.
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Title pretty much says it all. I'm just wondering if this makes a difference in the way VMs will process things and if one method is preferable vs. another.
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What is the difference between SAN, NAS and DAS?
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$ ps -Awwo pid,comm,args   PID COMMAND         COMMAND     1 init            /sbin/init     2 kthreadd        [kthreadd]     3 ksoftirqd/0     [ksoftirqd/0]     5 kworker/u:0     [kworker/u:0]     6 migration/0     [migration/0]     7 cpuset          [cpuset]     8 khelper         [khelper]     9 netns           [netns]    10 sync_supers     [sync_supers]    11 bdi-default     [bdi-default]    12 kintegrityd     [kintegrityd]    13 kblockd         [kblockd]    14 kacpid          [kacpid]    15 kacpi_notify    [kacpi_notify]    16 kacpi_hotplug   [kacpi_hotplug]    17 ata_sff         [ata_sff]    18 khubd           [khubd]   What do the brackets mean? Does args always return the full path to the process command (e.g. /bin/cat)?
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I see the different folders bin, dev, mnt, proc, srv, sys, etc.   What are the properties of all these different folders? What are their purposes? Are there files in some of them that I should not touch? Should I be touching files in the other folders?  Final question: in a Unix environment, do folders == directories? I apologize for all the questions.
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If I time a process using the time command, I get output for 'real', 'user', and 'sys'.  My understanding from  is that 'real' is wall time, whereas 'user' and 'sys' are process time.  Does this imply that 'user' and 'sys' will be unaffected by other processes? In other words, if the computer is under heavy load or light load from other processes, it may take more time on the wall clock ('real') to finish my process. But my process may have only required 5 seconds of running time, even though it was spread out over 20 seconds of real-world time.  Am I guaranteed that I'll be told '5 seconds user time' regardless of whatever else the system is doing?
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I have always found it difficult to find information about the system itself in Unix, whether it be   Which OS I am using (version number and all, to compare it with the latest available builds)? Which Desktop Environment am I using? If I am using KDE, most of the programs begin with a K and I can say I am using KDE, but there should be some way to query this, say from a script. Which kernel version am I using? (For example, I am using Fedora, and I want to know what Linux kernel version I am using)   Basically, what I miss is a single point/utility that can get all this information for me. Most of the times the solutions to the above would themselves be OS specific. Then, you are stuck.
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On the CLI, sometimes a command I type takes a while to complete, and sometimes I know when that's about to happen. I'm a bit confused on "backgrounding" and such in Linux.  What is the most common (or user-friendly way) of telling the CLI that I don't want to wait, please give me back my prompt immediately. And if it could give me a progress bar or just busy-spinner, that would be great!
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The idle task (a.k.a. swapper task) is chosen to run when no more runnable tasks in the run queue at the point of task scheduling. But what is the usage for this so special task? Another question is why i can't find this thread/process in the "ps aux" output (PID=0) from the userland?
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With commands like top and the gui based System Monitor I can see that at the moment I have several zombie processes.  What are zombie processes?  Do they affect the performance of the system or the application they are zombie to. Do they use too much memory or any memory at all?
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I need to understand the Linux versioning system and distribution concepts. what are public, stable or final terms for versions?
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I'm just beginning to dive into the internals of Linux, and I was wondering what the difference is between udev and the hal daemon.  From what I gather, both seem to be responsible for managing hot pluggable devices... is hald used by udev to listen, or are they two separate things?
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Is there an equivalent of the Unix  command in Windows?   So that I could figure out where commands I can run actually is.
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I'm not quite sure if stackoverflow or serverfault is the forum to use for this question, but ill try here.  Is there some command I can use or a file I can check in order to find out which process scheduler I'm using on my Linux system? I am not looking for the I/O scheduler, but the process scheduler, and please, do not refer to guides or howtos for what a scheduler is, what I'm simply asking is if there is a command or file I can run/check to see this. I could check the doc for my kernel but again I'm just wondering if there is a command or file i can check.  I might have been a little redundant above but that's because the posts I've seen people seem to confuse process scheduler with the i/o scheduler, and they don't seem to answer the actual question, just provide links to what a scheduler is which is not what I'm after here, so apologies if the above comments sounded rude.