Questions tagged [linux]
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.
37,168
questions
822
votes
2
answers
1.9m
views
How do I make `ls` show file sizes in megabytes?
What commands do I need for Linux's ls to show the file size in MB?
- 8,333
664
votes
7
answers
1.4m
views
Finding the PID of the process using a specific port?
I am installing hadoop on my Ubuntu system. When I start it, it reports that port 9000 is busy.
I used:
netstat -nlp|grep 9000
to see if such a port exists and I got this:
tcp 0 0 ...
- 7,077
565
votes
27
answers
839k
views
How can I resolve a hostname to an IP address in a Bash script?
What's the most concise way to resolve a hostname to an IP address in a Bash script? I'm using Arch Linux.
- 14.3k
503
votes
9
answers
373k
views
Execute vs Read bit. How do directory permissions in Linux work?
In my CMS, I noticed that directories need the executable bit (+x) set for the user to open them. Why is the execute permission required to read a directory, and how do directory permissions in Linux ...
- 6,093
432
votes
9
answers
202k
views
When should I not kill -9 a process?
I am always very hesitant to run kill -9, but I see other admins do it almost routinely.
I figure there is probably a sensible middle ground, so:
When and why should kill -9 be used? When and why ...
- 55.4k
401
votes
2
answers
807k
views
Compress a folder with tar?
I'm trying to compress a folder (/var/www/) to ~/www_backups/$time.tar where $time is the current date.
This is what I have:
cd /var/www && sudo tar -czf ~/www_backups $time"
I am ...
- 4,151
394
votes
3
answers
1.9m
views
How to check OS and version using a Linux command [duplicate]
What is the Linux command to check the server OS and its version?
I am connected to the server using shell.
- 4,051
388
votes
1
answer
870k
views
How do you empty the buffers and cache on a Linux system?
Prior to doing some benchmarking work how would one free up the memory (RAM) that the Linux Kernel is consuming for its buffers and cache?
Note that this is mostly useful for benchmarking. Emptying ...
slm♦
- 358k
387
votes
13
answers
423k
views
How to know whether Wayland or X11 is being used
So I just installed the latest Kali Linux on my laptop which was based on Debian 7 (oldstable). I then dist-upgrad-ed the whole thing to Debian 8.
I've always wanted Wayland instead of X11, so I ...
- 4,099
364
votes
12
answers
675k
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.
- 3,773
359
votes
18
answers
1.1m
views
How do I set my DNS when resolv.conf is being overwritten?
Most of the info I see online says to edit /etc/resolv.conf, but any changes I make there just get overridden.
$ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by ...
- 4,491
354
votes
11
answers
913k
views
How can I monitor disk io?
I'd like to do some general disk io monitoring on a debian linux server. What are the tools I should know about that monitor disk io so I can see if a disk's performance is maxed out or spikes at ...
- 3,765
350
votes
5
answers
636k
views
How to set default file permissions for all folders/files in a directory?
I want to set a folder such that anything created within it (directories, files) inherit default permissions and group.
Lets call the group "media". And also, the folders/files created within the ...
- 8,140
334
votes
27
answers
464k
views
How can I get my external IP address in a shell script?
I need to find my external IP address from a shell script. At the moment I use this function:
myip () {
lwp-request -o text checkip.dyndns.org | awk '{ print $NF }'
}
But it relies on perl-libwww,...
- 14.3k
330
votes
12
answers
642k
views
How to know number of cores of a system in Linux?
I wanted to find out how many cores my system has, so I searched the same question in Google. I got some commands such as the lscpu command.
When I tried this command, it gave me the following result:
...
- 3,505
286
votes
10
answers
402k
views
How to know if a disk is an SSD or an HDD
I want to know whether a disk is a solid-state drive or hard disk.
lshw is not installed. I do yum install lshw and it says there is no package named lshw. I do not know which version of http://pkgs....
- 10.1k
284
votes
9
answers
401k
views
How to display meminfo in megabytes in top?
Sometimes it is not comfortable to see meminfo in kilobytes when you have several gigs of RAM. In Linux, it looks like:
And here is how it looks in Mac OS X:
Is there a way to display meminfo in ...
- 7,054
282
votes
16
answers
1.1m
views
How do I find out what hard disks are in the system?
I need to know what hard disks are available, including ones that aren't mounted and possibly aren't formatted. I can't find them in dmesg or /var/log/messages (too much to scroll through). I'm hoping ...
- 56.8k
274
votes
2
answers
197k
views
Kernel inotify watch limit reached
I'm currently facing a problem on a linux box where as root I have commands returning error because inotify watch limit has been reached.
# tail -f /var/log/messages
[...]
tail: cannot watch '/var/...
- 3,023
273
votes
23
answers
415k
views
Efficiently delete large directory containing thousands of files
We have an issue with a folder becoming unwieldy with hundreds of thousands of tiny files.
There are so many files that performing rm -rf returns an error and instead what we need to do is something ...
- 3,863
270
votes
2
answers
230k
views
how can I recursively delete empty directories in my home directory? [duplicate]
Possible Duplicate:
How to remove all empty directories in a subtree?
I create directories very often, scattered over my home directory, and I find it very hard to locate and delete them.
I want ...
- 3,623
264
votes
6
answers
183k
views
What do the flags in /proc/cpuinfo mean?
How can I tell whether my processor has a particular feature? (64-bit instruction set, hardware-assisted virtualization, cryptographic accelerators, etc.) I know that the file /proc/cpuinfo contains ...
251
votes
4
answers
488k
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?
- 5,109
251
votes
3
answers
521k
views
Difference between cp -r and cp -a
I'm looking for the difference between cp -r and cp -a. What does "recursive" mean in terms of copying files from a folder?
- 2,619
251
votes
3
answers
386k
views
Linux "top" command: What are us, sy, ni, id, wa, hi, si and st (for CPU usage)?
When I issue top in Linux, I get a result similar to this:
One of the lines has CPU usage information represented like this:
Cpu(s): 87.3%us, 1.2%sy, 0.0%ni, 27.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0....
- 13.5k
249
votes
20
answers
321k
views
How can I get distribution name and version number in a simple shell script?
I'm working on a simple bash script that should be able to run on Ubuntu and CentOS distributions (support for Debian and Fedora/RHEL would be a plus) and I need to know the name and version of the ...
- 2,879
242
votes
11
answers
326k
views
How can I edit multiple files in Vim?
I know I can open multiple files with vim by doing something like vim 2011-12*.log, but how can I switch between files and close the files one at a time?
Also, how can I tell the file name of the ...
- 43.5k
242
votes
4
answers
586k
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?
- 2,761
241
votes
12
answers
626k
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 ...
- 18.9k
237
votes
11
answers
361k
views
Limit memory usage for a single Linux process
I'm running pdftoppm to convert a user-provided PDF into a 300DPI image. This works great, except if the user provides an PDF with a very large page size. pdftoppm will allocate enough memory to ...
- 2,473
232
votes
5
answers
957k
views
How to get the complete and exact list of mounted filesystems in Linux?
I usually use mount to check which filesystems are mounted. I also know there is some connection between mount and /etc/mtab but I'm not sure about the details. After reading How to check if /proc/ is ...
- 5,515
222
votes
7
answers
256k
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?
- 3,077
218
votes
1
answer
317k
views
How to skip "permission denied" errors when running find in Linux? [duplicate]
Possible Duplicate:
How do I remove “permission denied” printout statements from the find program?
When I run this command in Linux (SuSE):
find / -name ant
I get many error ...
- 2,419
215
votes
20
answers
236k
views
How to download portion of video with youtube-dl command?
I am using Ubuntu, and the youtube-dl command is working absolutely fine.
However, now I want to download only a portion a video that is too long. So I want to download only a few minutes of that ...
- 2,251
211
votes
4
answers
123k
views
Why do we use su - and not just su?
I don't understand why su - is preferred over su to login as root.
- 4,190
207
votes
8
answers
108k
views
Is Linux a Unix?
So, there are lots of different versions of Unix out there: HP-UX, AIX, BSD, etc. Linux is considered a Unix clone rather than an implementation of Unix. Are all the "real" Unices actual descendants ...
- 44.7k
200
votes
4
answers
213k
views
How do I determine the number of RAM slots in use?
I forgot how many RAM (DIMM) 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?
- 14.4k
195
votes
13
answers
552k
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 ...
- 2,371
190
votes
9
answers
191k
views
Why would someone choose FreeBSD over Linux? [closed]
Why would someone choose FreeBSD over Linux? What are the advantages of FreeBSD compared to Linux? (My shared hosting provider uses FreeBSD.)
- 2,223
187
votes
5
answers
249k
views
Understanding of diff output
I have file1.txt
this is the original text
line2
line3
line4
happy hacking !
and file2.txt
this is the original text
line2
line4
happy hacking !
GNU is not UNIX
if I do: diff ...
- 9,460
183
votes
5
answers
436k
views
Too many levels of symbolic links
I created this file structure:
test/src
test/firefox
When I run this command:
ln -s test/src test/firefox
I would expect a symbolic link test/firefox/src to be created pointing to test/src, ...
- 1,943
183
votes
3
answers
711k
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 ...
- 2,037
182
votes
21
answers
293k
views
Determine the size of a block device
How can I find out the size of a block device, such as /dev/sda? Running ls -l gives no useful information.
- 1,922
182
votes
13
answers
1.0m
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?
- 3,259
180
votes
5
answers
422k
views
How do I add X days to date and get new 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
...
yael
178
votes
9
answers
561k
views
What to do when a Linux desktop freezes?
I'm a Windows guy, dual booted recently, and now I'm using Linux Mint 12
When a Windows desktop freezes I refresh, or if I am using a program I use alt + F4 to exit the program or I can use ctrl + ...
- 4,034
173
votes
3
answers
190k
views
Linux: Difference between /dev/console , /dev/tty and /dev/tty0
On a Linux system, what is the difference between /dev/console, /dev/tty and /dev/tty0?
What is their respective use and how do they compare?
- 1,853
171
votes
9
answers
440k
views
Sorting down processes by memory usage
I am able to see the list of all the processes and the memory via
ps aux
and going through the VSZ and RSS
Is there a way to sort down the output of this command by the descending order on RSS ...
- 1,813
168
votes
7
answers
89k
views
Can I watch the progress of a `sync` operation?
I've copied a large file to a USB disk mounted on a Linux system with async. This returns to a command prompt relatively quickly, but when I type sync, of course, it all has to go to disk, and that ...
- 39k
165
votes
6
answers
164k
views
How do I read from /proc/$pid/mem under Linux?
The Linux proc(5) man page tells me that /proc/$pid/mem “can be used to access the pages of a process's memory”. But a straightforward attempt to use it only gives me
$ cat /proc/$$/mem /proc/self/...