18
votes
3answers
10k views

How to find out which (not installed) package a file belongs to?

On Debian systems (and derivatives): $ dpkg --search /bin/ls coreutils: /bin/ls That is, the file /bin/ls belongs to the Debian package named coreutils. But this only works if the package is ...
9
votes
4answers
44k views

Storing output of command in shell variable [duplicate]

I have an operation using cut that I would like to assign result to a variable var4=echo ztemp.xml |cut -f1 -d '.' I get the error: ztemp.xml is not a command The value of var4 never gets ...
8
votes
2answers
11k views

Why is my variable local one 'while read' loop, but not in another seemingly similar loop?

Why do I get different values for $x from the snippets below? #!/bin/bash x=1 echo fred>junk ; while read var ; do x=55 ; done <junk echo x=$x # x=55 .. I'd expect this result x=1 cat ...
39
votes
4answers
8k views

What does size of a directory mean in output of 'ls -l' command?

What does size of a directory mean in output of ls -l command?
6
votes
2answers
4k views

Why is there a discrepancy in disk usage reported by df and du? [duplicate]

I have a Linux(CentOS) server, the OS+packages used around 5GB. Then, I transferred 97GB data from a Windows server to two folders on this Linux server, after calculated the disk usage, I see the ...
11
votes
4answers
7k views

32-bit, 64-bit CPU op-mode on Linux

I'm confused. Running Fedora Linux, lscpu yields: Architecture: i686 CPU op-mode(s): 32-bit, 64-bit ... But when I try to install a 64-bit program (Chrome) I get error like: ...
113
votes
3answers
65k views

What does “LC_ALL=C” do?

What does the C value for LC_ALL do in Unix-like systems? I know that it forces the same locale for all aspects but what does C do?
31
votes
1answer
7k views

When is double-quoting necessary?

The old advice used to be to double-quote any expression involving a $VARIABLE, at least if one wanted it to be interpreted by the shell as one single item, otherwise, any spaces in the content of ...
53
votes
4answers
48k views

Reserved space for root on a filesystem - why?

I understand that by default, newly created filesystems will be created with 5% of the space allocated for root. I also know you can change the defined space with: tune2fs -m 1 /dev/sdXY What I'm ...
37
votes
5answers
12k views

When would you use an additional file descriptor?

I know you can create a file descriptor and redirect output to it. e.g. exec 3<> /tmp/foo # open fd 3. echo a >&3 # write to it exec 3>&- # close fd 3. But you can do the same ...
33
votes
13answers
15k views

Is there a robust command line tool for processing csv files?

I work with CSV files and sometimes need to quickly check the contents of a row or column from the command line. In many cases cut, head, tail, and friends will do the job; however, cut cannot easily ...
20
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 ...
56
votes
3answers
14k views

Why is there a big delay after entering a wrong password?

I notice a weird (well, according to me) thing about passwords. For example, if I type an incorrect password during login, there will be a few seconds' delay before the system tells me so. When I try ...
33
votes
8answers
8k views

Is there a way to modify a file in-place?

I have a fairly large file (35Gb), and I would like to filter this file in situ (i.e. I don't have enough disk space for another file), specifically I want to grep and ignore some patterns — is there ...
26
votes
3answers
4k views

What is the difference between these commands for bringing down a Linux server?

Reading "What is the difference between Halt and Shutdown commands?" , I generally have an idea what does the command shutdown does, with or without -h/-r options. The "halt" command performs ...
4
votes
1answer
40k views

How can I fix/install/reinstall grub?

So I started out with a 250GB HDD, the stock drive from an EeePC 1015pem that I am trying to turn into a MintBook. The drive is physically operable, but all data has been nuked, including the old OS. ...
122
votes
21answers
109k views

How can I get my external IP address in bash?

I need to find my external IP address from a bash script. At the moment I use this function: myip () { lwp-request -o text checkip.dyndns.org | awk '{ print $NF }' } But it depends on ...
116
votes
9answers
12k views

The myths about malware in Unix / Linux

Is it possible for my Linux box to become infected with a malware? I haven't heard of it happening to anyone I know, and I've heard quite a few times that it isn't possible. Is that true? If so, ...
39
votes
8answers
155k 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?
48
votes
7answers
9k views

Is there a one-liner that allows me to create a directory and move into it at the same time?

I find myself repeating a lot of: mkdir longtitleproject cd longtitleproject Is there a way of doing it in one line without repeating the directory name? I'm on bash here.
35
votes
5answers
33k views

How to determine which process is creating a file?

Given file path, how can I determine which process creates it (and/or reads/writes to it)?
4
votes
2answers
1k views

What information do I need to solve an APT dependency issue?

I've seen several times people with unmet dependencies, which apt-get doesn't tells straightforward what's the problem, like this one: The following packages have unmet dependencies: ...
21
votes
2answers
7k views

Does (should) LC_COLLATE affect character ranges?

Collation order through LC_COLLATE defines not only the sort order of individual characters, but also the meaning of character ranges. Or does it? Consider the following snippet: unset LANGUAGE ...
10
votes
2answers
5k views

real memory usage

if I understand correctly, in the following output produced by free, 3535m is the actual free memory available to applications, only 413m is used, is this correct? need some clarification on the ...
115
votes
1answer
150k 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 ...
98
votes
8answers
16k views

Which is the safest way to get root privileges: sudo, su or login?

I would like to have the root account in safety even if my unprivileged user is compromised. On Ubuntu you can only use sudo for "security reasons" by default. However I am not sure it is any safer ...
54
votes
4answers
7k views

In what order do piped commands run?

I've never really thought about how the shell actually executes piped commands. I've always been told that the "stdout of one program gets piped into the stdin of another," as a way of thinking about ...
63
votes
5answers
21k views

What's the point in adding a new line to the end of a file?

Some compilers (especially C or C++ ones) give you warnings about: No new line at end of file I thought this would be a C-programmers-only problem, but github displays a message in the commit view: ...
46
votes
10answers
37k views

How to test what shell I am using in a terminal?

How to check what shell I am using in a terminal? What is the shell I am using in MacOS?
30
votes
8answers
40k views

Different ways to execute a shell script

There a several ways to execute a script, the ones I know are: /path/to/script # using the path (absolute or relative) . script # using the . (dot) source script # using the `source` command ...
34
votes
10answers
23k views

How to understand what's taking up space?

I'm looking for a linux alternative to WinDirStat. I would like to know what is taking up space on my hard drives. A program that works on console and doesn't require a UI is preferred .
31
votes
4answers
95k views

SSH login with clear text password as a parameter? [duplicate]

I need to login to a user that I've created on a remote host running Ubuntu. I can't use an ssh key because the ssh login will happen from a bash script ran within a server that I won't have access to ...
26
votes
8answers
56k views

Changing extension to multiple files

I would like to change file extension from *.txt file to *.text file, tried using the basename command, but I am having trouble on changing more than 1 file, I am getting a basename: too many ...
25
votes
2answers
13k views

What mount points exist on a typical Linux system?

I have 2 questions. During Linux installation we specify memory space for 2 mount points - root and swap. Are there any other mount points created without the users notice? Is this statement ...
11
votes
4answers
7k views

What should I do before dual-booting Windows 7 and Debian on EFI?

I'm about to purchase an Asus motherboard with EFI firmware and wanted to prepare myself for installing Windows and Debian once the hardware arrives. I was hoping that someone who has gone down this ...
18
votes
4answers
6k views

The merits of a partitionless filesystem

I ran into something a couple of weeks ago that I'd never seen before: A filesystem (ext3 I believe) installed to a storage device without a partition. In essence /dev/sdb was the entire filesystem. I ...
20
votes
3answers
2k views

gnu find and masking the {} for some shells - which?

The man page for gnu find states: -exec command ; [...] The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, ...
9
votes
4answers
9k views

How do I connect to a pc through another pc using ssh

I have three Computers. PC1 and PC2 is on a private LAN, where PC1 is known to PC2 as 192.168.0.2 PC2 and PC3 is on a another LAN, where PC2 is known to PC3 as 192.168.123.101 How can I connect to ...
39
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 ...
18
votes
2answers
64k views

How can I assign the output of a command to a shell variable?

I want to assign the result of an expression to a variable and concatenate it with a string, then echo it. Here's what I've got: #!/bin/bash cd ~/Desktop; thefile= ls -t -U | grep -m 1 "Screen Shot"; ...
18
votes
6answers
2k views

How can I cleanly add to $PATH?

I'd like a way to add things to $PATH, system-wide or for an individual user, without potentially adding the same path multiple times. One reason to want to do this is so that additions can be made ...
6
votes
1answer
483 views

How to change the forgotten root password?

I am very new to Debian linux, I forgot my root password...actually I think I know what it is because it is the same password I have for pretty much everything but in the Terminal in tell me "Sorry, ...
4
votes
1answer
524 views

Difference between ' and " on command line (bash)?

I used to use '' and "" interchangeably on the command line, but I recently noticed that '$HOME/some/dir' is not expanded, while "$HOME/some/dir" is. I searched around a little bit and found that "" ...
2
votes
1answer
3k views

“No such file or directory” lies on Optware installed binaries

I've been using Optware to install packages on my ARM-based NAS for a while - the usual stuff like Transmission, Samba and others. However, I'd been having problems with Transmission hanging not long ...
291
votes
9answers
116k 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 ...
128
votes
6answers
278k views

How to forward X over SSH from Ubuntu machine?

I have a machine running Ubuntu which I SSH to from my Fedora 14 machine. I want to forward X from the Ubuntu machine back to Fedora so I can run graphical programs remotely. Both machines are on a ...
87
votes
2answers
19k views

Why do we use su - and not just su?

I don't understand why su - is preferred over su to login as root.
92
votes
7answers
9k views

Why is cd not a program?

I've always wondered why cd isn't a program, but never managed to find the answer. Anyone know why this is the case?
33
votes
4answers
4k views

What are the responsibilities of each Pseudo-Terminal (PTY) component (software, master side, slave side)?

I am trying to figure out how a tty works1 (the work-flow and responsibilities of each elements). I have read several interesting articles about it, but there are still some blurry areas. This is ...
77
votes
13answers
51k views

how do you sort du output by size?

How do you sort du -sh /dir/* by size? I read one site that said use | sort -n but that's obviously not right. Here's an example that is wrong. [~]# du -sh /var/* | sort -n 0 /var/mail 1.2M ...

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