These questions are about Linux in general -- NOT specific to a particular distribution. If the question just happens to be in a Linux environment, please specify your Linux distribution in the body of your question, but do NOT use the /linux tag.

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50
votes
5answers
38k views

How can I tell what version of Linux I'm using?

Often times I will ssh into a new client's box to make changes to their website configuration without knowing much about the server configuration. I have seen a few ways to get information about the ...
50
votes
4answers
17k views

Why is video tearing such a problem in Linux?

I've used many variants of Linux(mostly Debian derivatives) for over a decade now. One problem that I haven't seen solved satisfactorily is the issue of horizontal tearing, or Vsync not being ...
49
votes
3answers
176k views

How can get a list of all scheduled cron jobs on my machine?

My sysadmin has set up a bunch of cron jobs on my machine. I'd like to know exactly what is scheduled for what time. How can I get that list?
48
votes
6answers
33k views

How can I see dmesg output as it changes?

I'm writing a device driver that prints error message into ring buffer dmesg output. I want to see the output of dmesg as it changes. How can I do this?
47
votes
11answers
27k views

Recommended reading to better understand Unix/Linux internals [closed]

I've worked on *nix environments for the last four years as a application developer (mostly in C). Please suggest some books/blogs etc. for improving my *nix internals knowledge.
47
votes
7answers
115k views

How to list all files ordered by size

I would like to list all files in the order of big to small in size and the files could be present anywhere in a certain folder.
46
votes
7answers
73k views

Uploading directories with sftp?

I'm having some trouble uploading directories(which contain other directories a few levels deep) by sftp. I realize I could work around this by gzipping, but I don't see why that's necessary. Anyway, ...
45
votes
11answers
29k views

How do I find how long ago a Linux system was installed?

How can I find the time since a Linux system was first installed, provided that nobody has tried to hide it?
45
votes
5answers
49k views

Creating a ram disk on Linux

I have a machine with 62GB of RAM, and a trunk that's only 7GB, so I thought I would create a RAM disk and compile there. I am not a Linux expert. I found instructions on the internet to create the ...
45
votes
2answers
46k views

Difference between pts and tty

Possible Duplicate: What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'? I always see pts and tty when I use the who ...
45
votes
9answers
186k views

Unix/Linux undelete/recover deleted files

Is there a command to recover/undelete deleted files by rm? $ rm -rf /path/to/myfile How can I recover myfile? If there is such a tool how can I use it?
44
votes
8answers
141k views

How to determine Linux kernel architecture?

uname -m gives i686 and uname -m gives i686 i386 output in Red Hat Enterprise Linux Server release 5.4 (Tikanga) machine. I need to install Oracle Database 10g Release 2 on that machine. So, how can I ...
43
votes
3answers
6k views

On Linux, when does “uptime” start counting from?

My computer says: $ uptime 10:20:35 up 1:46, 3 users, load average: 0,03, 0,10, 0,13 And if I check last I see: reboot system boot 3.19.0-51-generi Tue Apr 12 08:34 - 10:20 (01:45) ...
43
votes
11answers
45k views

How can I reliably get the operating system's name?

Say I am logged into a remote system, how can I know what it's running? On most modern Linuxes (Linuces?), you have the lsb_release command: $ lsb_release -ic Distributor ID: LinuxMint Codename: ...
43
votes
3answers
15k views

What is the difference between procfs and sysfs?

What is the difference between procfs and sysfs? Why are they made as file systems? As I understand it, proc is just something to store the immediate info regarding the processes running in the ...
43
votes
4answers
65k views

Manually generate password for /etc/shadow

I need to manually edit /etc/shadow to change the root password inside of a virtual machine image. Is there a command-line tool that takes a password and generates an /etc/shadow compatiable password ...
42
votes
2answers
87k views

timestamp, modification time, and created time of a file

I just know that ls -t and ls -f give different sorting of files and subdirectories under a directory. What are the differences between timestamp, modification time, and created time of a file? How ...
42
votes
9answers
14k views

Easy incremental backups to an external hard drive

For a while I used Dirvish to do incremental backups of my machines, but it is slightly cumbersome to configure, and if you do not carry a copy of your configuration it can be hard to reproduce ...
41
votes
7answers
12k views

Software developer switching from Linux to OS X, what are the gotchas?

I have used Ubuntu/Fedora/Red Hat/Suse but haven't used OS X at all. If I have to start using OS X regularly, what are the things I should look out for? Tools I use are GNU tool chain, C++/Boost, ...
41
votes
3answers
21k views

Shell: how to go to the beginning of line when you are inside a screen?

I am inside a screen (screen -Ra). I have a long command, and I am at the end. Instead of keeping the left arrow, how can you go to the beginning of the line? CTRL-A works when I am in a normal ...
41
votes
7answers
31k views

Linux Kernel: Good beginners' tutorial [closed]

I'm interested in modifying the kernel internals, applying patches, handling device drivers and modules, for my own personal fun. Is there a comprehensive resource for kernel hacking, intended for ...
41
votes
5answers
28k views

Can Linux deal with ultra high resolution displays?

A few months ago, Samsung announced the Ativ Book 9 Plus, a pretty cool ultrabook with a screen resolution of 3200 x 1800 pixels (QHD+). The device ships with Windows 8 until Windows 8.1 is released ...
40
votes
4answers
5k views

unix, difference between path starting with '/' and '//'

In unix/linux, any number of consecutive forwardslashes in a path is generally equivalent to a single forwardslash. eg. $ cd /home/shum $ pwd /home/shum $ cd /home//shum $ pwd /home/shum $ cd ...
40
votes
7answers
10k views

Why does mount require root privileges?

Why does Linux require that a user be root/using sudo/specifically authorized per mount in order to mount something? It seems like the decision as to whether to allow a user to mount something should ...
40
votes
9answers
60k views

Linux distribution geared towards developers [closed]

I am looking for the best flavor of Linux that would appeal to the developer's side of me. I am a lover of open source and use several different languages. Is there such a thing as a Linux geared ...
39
votes
11answers
71k views

List partition labels from the command line

Is there a command that will list all partitions along with their labels? sudo fdisk -l and sudo parted -l don't show labels by default. EDIT: (as per comment below) I'm talking about ext2 labels - ...
39
votes
5answers
26k views

Difference Between cp -r and cp -R (copy command)

cp- r is meant to copy files recursively, and cp -R for copying directories recursively. But I've checked, and both appear to copy both files and directories, the same thing. So, what's the difference ...
39
votes
4answers
36k views

Moving linux install to a new computer

I know that it can, in some circumstances, be difficult to move a Windows installation from one computer to another (physically move the hard drive), but how does that work on linux? Aren't most of ...
38
votes
4answers
5k views

Why is Linux commonly used as operating system for supercomputers?

As of november 2010, Linux is used on 459 out of the 500 supercomputers of the TOP500. What are the reasons behind this massive use of Linux in the supercomputer space?
38
votes
2answers
88k views

What does aux mean in `ps aux`?

ps aux seems to conveniently list all processes and their status and resource usage (Linux/BSD/MacOS), however I cannot comprehend the meaning of parameter aux using man ps. What does aux mean?
38
votes
2answers
19k views

What is this new /run filesystem?

I just ran df -h a minute ago and noticed a filesystem has been added that I'm not familiar with. Does anyone know why /run exists? Is this something that's been added by the kernel? By Arch Linux? ...
38
votes
3answers
22k views

What are pseudo terminals (pty/tty)?

This might be really basic question but I want to understand it thoroughly. What is a pseudo terminal? (tty/pty) Why do we need them? How they got introduced and what was the need for it? Are they ...
37
votes
9answers
21k views

Why put things other than /home to a separate partition?

So recently a Debian 5.0.5 installer offered me to have separate /usr, /home, /var and /tmp partitions (on one physical disk). What is the practical reason for this? I understand that /home can be ...
37
votes
5answers
84k views

linux: How can I view all UUIDs for all available disks on my system?

My /etc/fstab contains this: # / was on /dev/sda1 during installation UUID=77d8da74-a690-481a-86d5-9beab5a8e842 / ext4 errors=remount-ro 0 1 There are several other disks on ...
37
votes
4answers
10k views

How can I mount a block device from one computer to another via the network as a block device?

Is it possible to export a block device such as a DVD or CDROM and make it so that it's mountable on another computer as a block device? NOTE: I'm not interested in doing this using NFS or Samba, I ...
37
votes
7answers
12k views

Block network access of a process?

Is it possible to block the (outgoing) network access of a single process?
37
votes
4answers
46k views

What's the best way to join files again after splitting them?

If I have a large file and need to split it into 100 megabyte chunks I will do split -b 100m myImage.iso That usually give me something like xaa xab xac xad And to get them back together I have ...
37
votes
5answers
20k views

What is the difference between kernel drivers and kernel modules?

When I do a lspci -k on my Kubuntu with a 3.2.0-29-generic kernel I can see something like this: 01:00.0 VGA compatible controller: NVIDIA Corporation G86 [Quadro NVS 290] (rev a1) Subsystem: ...
37
votes
5answers
42k views

How to reconnect a logically disconnected USB device?

It is possible for a USB storage device to become logically disconnected: the device is still plugged in, but is invisible from the operating system (e.g. it's not listed under /proc/bus/usb). Maybe ...
36
votes
7answers
37k views

Disable screen blanking on text console

I'm running linux clusters, mostly on SLES10. The servers are mostly blades, accessed via remote console. There is a real console in the server room, but switched off. I would like to disable the ...
36
votes
3answers
18k views

A list of available DBus services

Is there such a thing as list of available DBus services? I've stumbled upon a few (like those provided by NetworkManager, Rhythmbox, Skype, HAL). I wonder if I can find a rather complete list of ...
36
votes
4answers
40k views

How to attach terminal to detached process?

I have detached a process from my terminal, like this: $ process & That terminal is now long closed, but process is still running and I want to send some commands to that process's stdin. Is ...
36
votes
3answers
167k views

Timezone setting in Linux [closed]

I'm setting the timezone to GMT+6 on my Linux machine by copying the zoneinfo file to /etc/localtime, but the date command is still showing the time as UTCtime-6. Can any one explain to me this ...
36
votes
6answers
60k views

disable transparent hugepages

We are installing SAP HANA in a RAID machine. As part of the installation step, it is mentioned that, To disable the usage of transparent hugepages set the kernel settings at runtime with echo ...
36
votes
8answers
62k views

Correctly determining memory usage in Linux

I'm a bit confused on some of the results I am seeing from ps and free. On my server, this is the result of free -m [root@server ~]# free -m total used free shared ...
36
votes
4answers
30k views

How to Determine the Amount of RAM Slots In Use?

I forgot how many RAM modules are installed on my laptop. I do not want to unscrew it but want to look it up on the console using bash. How do I gather this information?
36
votes
11answers
16k views

A tool for automatically applying RandR configuration when external display is plugged in

is there a tool which enables one to: remember current RandR configuration (position, orientation, resolution etc) on per-monitor basis, automatically apply last known good configuration as soon as ...
36
votes
7answers
2k views

ZFS under Linux, does it work?

Could I get ZFS to work properly in Linux? Are there any caveats / limitations?
35
votes
5answers
102k views

Can I set up system mail to use an external SMTP server?

Is it possible to set up system mail on a linux box to be sent via a different smtp server - maybe even with authentication? If so, how do I do this? If that's unclear, let give an example. If I'm at ...
34
votes
3answers
30k views

What is stored in /dev/pts files and can we open them?

According to my knowledge, /dev/pts files are created for ssh or telnet sessions.