Questions specifically about Linux but not specific to a particular distribution. If the question could apply to any Unix-like system, specify your Linux distribution in the body of your question but do not use the /linux tag.

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21
votes
6answers
39k views

Linux ls to show only filename date and size

How can I use ls in linux to get a listing of filenames date and size only. I don't need to see the other info such as owner or permission. Is this possible?
21
votes
8answers
5k views

The most universal scripting language for Linux is?

We are writing scripts for Linux systems, there has been some debate over what would be the most universally Linux present scripting language to use. Bash, SH, Posix? What?
21
votes
3answers
71k views

linux + add X days to date and get new virtual date

I have Linux ( RH 5.3) machine I need to add/calculate 10 days plus date so then I will get new date (expiration date)) for example # date Sun Sep 11 07:59:16 IST 2012 So I need to get ...
21
votes
6answers
22k views

Execute a specific command in a given directory without cd'ing to it?

Is there a way to execute a command in a different directory without having to cd to it? I know that I could simply cd in and cd out, but I'm just interested in the possibilities of forgoing the extra ...
21
votes
3answers
8k views

Why does Linux use a swap partition rather than a file?

It seems to me a swap file is more flexible.
21
votes
6answers
4k views

How to safely turn off swap permanently? (on Debian Jessie)

I fresh installed Debian Jessie with default partitioning on an SSD drive. My current disk partitions look like this: As I have 16GB RAM, I think I don't need swap. On Windows, I had it turned off ...
21
votes
3answers
1k views

Linux Debian codenames

I've got a few, quite silly, non-technical questions about giving codenames to Debian releases. Each Debian release has its unique codename, which is (so far) a characters' name from Toy Story movies ...
21
votes
3answers
78k views

How to rename multiple files in single command or script in Unix? [duplicate]

I have the below list of files aro_tty-mIF-45875564pmo_opt aro_tty-mIF-45875664pmo_opt aro_tty-mIF-45875964pmo_opt aro_tty-mIF-45875514pmo_opt aro_tty-mIF-45875524pmo_opt that I need to rename to ...
21
votes
4answers
23k views

sending text input to a detached screen

I'm trying to run a minecraft server on my unRAID server. The server will run in the shell, and then sit there waiting for input. To stop it, I need to type 'stop' and press enter, and then it'll ...
21
votes
6answers
3k views

How to achieve portability with sed -i (in-place editing)?

I'm writing shell scripts for my server, which is a shared hosting running FreeBSD. I also want to be able to test them locally, on my PC running Linux. Hence, I'm trying to write them in a portable ...
21
votes
2answers
13k views

/proc/PID/fd/X link number

In Linux, in /proc/PID/fd/X, the links for file descriptors that are pipes or sockets have a number, like: l-wx------ 1 user user 64 Mar 24 00:05 1 -> pipe:[6839] l-wx------ 1 user user 64 Mar 24 ...
21
votes
4answers
22k views

What is the equivalent of Active Directory on Linux

I have a couple of machines at home (plus a number of Linux boxes running in VMs) and I am planning to use one of them as a centralized file server. Since I am more a Linux user rather than a ...
21
votes
3answers
12k views

Determining Specific File Responsible for High I/O

This is a simple problem but the first time I've ever had to actually fix it: finding which specific files/inodes are the targets of the most I/O. I'd like to be able to get a general system overview, ...
21
votes
5answers
42k views

How to know which Linux and which version I am using

When I run cat /proc/version command in terminal, I got below output: Linux version 2.6.18-348.1.1.0.1.el5 (mockbuild@ca-build56.us.oracle.com) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)) #1 SMP ...
21
votes
1answer
24k views

What is kernel ip forwarding?

I have seen on many blogs, using this command to enable IP forwarding while using many network security/sniffing tools on linux echo 1 > /proc/sys/net/ipv4/ip_forward Can anyone explain me in ...
21
votes
5answers
6k views

Corruption-proof SD card filesystem for embedded Linux?

Recently we had a rather unpleasant situation with our customer - Raspberry Pi based "kiosk" used to display remote sensing data (nothing more fancy than a kiosk mode browser displaying a ...
21
votes
2answers
9k views

How to blacklist a correct bad RAM sector according to MemTest86+ error indication?

MemTest86+ (the version included with Ubuntu 13.04) says Failing address: 002f796c48 - 759.5 MB What should I specify in the memmap kernel parameter to bypass this area? I've tried running ...
21
votes
2answers
17k views

How to colorize output of ls ?

I'm running CentOS in Linux text mode. When I run the command ls /usr/, the output is too hard to read (dark blue on black). How can I change the text coloring?
21
votes
3answers
7k views

Why does the 'bin' user need a login shell?

During an audit of /var/log/auth.log on one of my public webservers, I found this: Jan 10 03:38:11 Bucksnort sshd[3571]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 ...
21
votes
2answers
6k views

How does one change the delay that occurs after entering an incorrect password?

After entering an incorrect password at a login prompt, there s an approximately 3-second delay. How can I change that on a Linux system with PAM?
21
votes
2answers
6k views

How does sudo remember you already entered root's password?

When using sudo on Linux, it asks for root password, but only the first time you run it. If you run another sudo command, it remember you already entered the password previously and doesn't ask for ...
21
votes
4answers
1k views

Making Linux read swap back into memory

The Linux kernel swaps out most pages from memory when I run an application that uses most of the 16GB of physical memory. After the application finishes every action (typing commands, switching ...
20
votes
6answers
4k views

Why do most linux distros default gnome? [closed]

Why the default desktop environment of most popular linux distros is gnome? KDE seems to me an equally good desktop environment. Is it for licence reason? historic? or else?
20
votes
8answers
33k views

How to determine which sd* is usb? [duplicate]

Possible Duplicate: How to know if /dev/sdX is a connected USB or HDD? The output of ls /dev/sd* on my system is - sda sda1 sda2 sda3 sda4 sda5 sda6 sda7 sdb sdc sdc1 sdc2 ...
20
votes
4answers
2k views

Is there a reason why 'owner' permissions exist? Aren't group permissions enough?

I think I rather understand how file permissions work in linux. However, I don't really understand why they are split into three levels and not into two. I'd like the following issues answered: Is ...
20
votes
3answers
28k views

Linux network troubleshooting and debugging

From time to time Linux and Unix users faced with various network problems. Many of these problems are presented here and at some others troubleshooting forums, but the are very concrete and contains ...
20
votes
4answers
7k views

Why does dd from /dev/random give different file sizes?

I am running the following command on an ubuntu system: dd if=/dev/random of=rand bs=1K count=2 However, every time I run it, I end up with a file of a different size. Why is this? How can I ...
20
votes
3answers
37k views

Yum: How can I view variables like $releasever, $basearch & $YUM0?

I am setting up a yum repository, and need to debug some of the URLs in the yum.conf file. I need to know why is Scientific Linux trying to grab this URL, when I was expecting it to grab another URL: ...
20
votes
4answers
27k views

What is a spinlock in Linux?

I would like to know about spinlocks in detail? Could someone explain that to me?
20
votes
4answers
80k views

Why the default eth0 interface is down by default on CentOS?

I am already a little bit familiar with Linux distros like Debian or Ubuntu (yeah, very similar) but I wanted to try Red Hat based - CentOS 6.2 . I have installed it on my Windows 7 host in virtualBox ...
20
votes
6answers
37k views

How to see disk details like manufacturer in Linux

With sfdisk -s I can see the disk capacity as follows: $ sfdisk -s /dev/cciss/c0d0: 143338560 total: 143338560 blocks How do I see disk details like disk manufacturer? I tried hdparm, but got an ...
20
votes
2answers
13k views

How to update linux “locate” cache

How can i update the cache / index of locate? I installed new packages and the files are clearly not yet indexed. So which command do I have to ommit, in order for the indexer to trigger. I'm ...
20
votes
4answers
6k views

Linux: Kill process based on arguments

How can I kill a process based on its command line arguments? killall, pgrep, and pkill seem to only work based on the process name. I need this to be able to differentiate between a number of ...
20
votes
6answers
23k views

How to find which process is regularly writing to disk?

How can I find which process is constantly writing to disk? I like my workstation to be close to silent and I just build a new system (P8B75-M + Core i5 3450s -- the 's' because it has a lower max ...
20
votes
2answers
55k views

ifconfig command not found

I've just installed CentOS7 as a virtual machine on my mac (osx10.9.3 + virtualbox) .Running ifconfig returns command not found. Also running sudo /sbin/ifconfig returns commmand not found. I am root. ...
20
votes
4answers
16k views

How to check that AES-NI is supported by my CPU?

Howcan I check if my CPU supports the AES-NI instruction set under Linux/UNIX.
20
votes
3answers
25k views

Where can I see a list of kernel killed processes?

Is there some way I can check which of my processes the kernel has killed? Sometimes I log onto my server and find that something that should've run all night just stopped 8 hours in and I'm unsure if ...
20
votes
2answers
33k views

What is the difference between ioctl(), unlocked_ioctl() and compat_ioctl()?

Going through the linux 2.6.36 source code at lxr.linux.no, I could not find the ioctl() method in file_operations. Instead I found two new calls: unlocked_ioctl() and compat_ioctl(). What is the ...
20
votes
4answers
11k views

Block Particular Command in Linux for Specific user

How to block command, let say mkdir for specific user ? What I did just created read-only function and store in users profile ~/.bashrc /bin/mkdir() { echo "mkdir command not allow for you" ...
20
votes
6answers
3k views

Is there a way to limit overall CPU consumption?

My laptop (an HP with an i3 chip) overheats like crazy every time I run a resource heavy process (like a large compilation, extracting large tarballs or ... playing Flash). I am currently looking ...
20
votes
7answers
13k views

Linux boot loaders supporting full disk encryption?

Are there any Linux boot loaders supporting full disk encryption (a la TrueCrypt). I know there was work towards adding encryption support to GRUB2, but this does not seem to be ready yet. Any other ...
20
votes
1answer
3k views

Who creates /etc/{group,gshadow,passwd,shadow}-?

In any linux system I have access to (a couple of Archlinuxes, an Ubuntu, a Debian Sid and a Gentoo) there are the following 4 files in /etc/, all ending with a dash: /etc/group- /etc/gshadow- ...
20
votes
1answer
13k views

What is maximum RAM supportable by Linux?

What is the maximum supportable RAM by Linux? Assume that hardware is/supports 64-bit. Among all Linux distros. Does it go up to 16 exabytes, or is it limited like with Windows which I believe is 192 ...
19
votes
5answers
1k views

Commands to learn about an unfamiliar system [closed]

You log in to an unfamiliar UNIX or Linux system (as root). Which commands do you run to orient yourself and figure out what kind of system you are on? How do you figure out what type of hardware is ...
19
votes
3answers
4k views

Standard and/or common directories on Unix/Linux OSes

Coming from the Windows world, I have found the majority of the folder directory names to be quite intuitive: \Program Files contains files used by programs (surprise!) \Program Files (x86) contains ...
19
votes
3answers
53k views

How can I benchmark my HDD?

I've seen commands to benchmark one's HDD such as this using dd: $ time sh -c "dd if=/dev/zero of=ddfile bs=8k count=250000 && sync" Are there better methods to do so than this?
19
votes
4answers
1k views

Why does Linux scale so well to different hardware platforms?

Why does Linux run well on so many different types of machines - desktops, laptops, servers, embedded devices, mobile phones, etc? Is it mainly because the system is open, so any part of it can be ...
19
votes
3answers
38k views

show gateway IP address when performing ifconfig command

Currently, when using the ifconfig command, the following IP addresses are shown: own IP, broadcast and mask. Is there a way to show the related gateway IP address as well (on the same screen with ...
19
votes
2answers
55k views

Convert Amazon .pem key to Putty .ppk key Linux

I have generated and downloaded a private .pem key from AWS. However, to use Putty in order to connect to the virtual machine, I must have that key in .ppk format. The process of conversion is ...
19
votes
3answers
31k views

What is the most high-performance Linux filesystem for storing a lot of small files (HDD, not SSD)?

I have a directory tree that contains many small files, and a small number of larger files. The average size of a file is about 1 kilobyte. There are 210158 files and directories in the tree (this ...