23
votes
6answers
14k 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 ...
19
votes
8answers
12k 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 ...
18
votes
3answers
5k views

How can I use two bash commands in -exec of find command?

Is it possible to use 2 commands in the -exec part of find command ? I've tried something like: find . -name "*" -exec chgrp -v new_group {} ; chmod -v 770 {} \; and I get: find: missing ...
14
votes
7answers
16k views

Which GUI diff viewer would you recommend?

I've hardly ever used anything other than Meld. Can you recommend anything else? It would be extra nice if you give a reason for your recommendation (as a Comment). [note] I want an alternative ...
6
votes
8answers
3k views

Automatically run commands over SSH on many servers

There is a list of IP addresses in a .txt file, ex.: 1.1.1.1 2.2.2.2 3.3.3.3 Behind every IP address there is a server, and on every server there is an sshd running on port 22. Not every server is ...
22
votes
4answers
4k views

Is Mac OS X UNIX?

I have this argument recently saying Mac OS X was not UNIX, but Unix-like. I know there is a Single Unix Specification and those spec complaint could use the UNIX trade mark. Is Mac OS X an UNIX ...
21
votes
4answers
9k views

Determine which process is creating a file

Given file path, how can I determine which process creates it (and/or reads/writes to it)?
11
votes
9answers
3k views

Ensure a process is always running

I started hosting sites a while back using Cherokee. For external sources (FastCGI, etc) it has an option to launch the process if it can't find one running on the designated socket or port. This is ...
3
votes
6answers
1k views

Common multiple SSH connections file handling issue

often I have to download a file that isn't directly accessable via the first SSH connection. For example I'm on a Windows machine and I want to access another machine that is only accessable from lan. ...
15
votes
6answers
425 views

Reading and searching long man pages

I finally got fed up when wanting to read about bash's read and it's -s option with man bash. I found the right spot eventually (around line 4500), but it was a frustrating as usual, since both /read ...
14
votes
3answers
4k views

How to list files that were changed in a certain range of time?

How can I list recursively all files that were changed between 22.12.2011 and 24.12.2011?
10
votes
2answers
2k views

Correctly setting environment

I'm using zsh and gdm to run gnome. Some time ago I discovered that variables are not set correctly. For example LANG/LC_ALL are incorrect ("" instead of en_GB.UTF-8). I split the .zshrc into .zshrc ...
10
votes
1answer
4k views

What is meant by mounting a device in Linux?

I've heard the term "mounting" when referring to devices in Linux. What is its actual meaning? How it handling now unlike older versions? I haven't done that manually via the command-line. Can you ...
8
votes
4answers
533 views

Bash- detect init system

This may have more to do with detecting operating systems, but I specifically need the init system currently in use on the system. Fedora 15 now uses systemd, Ubuntu uses Upstart, while others use ...
7
votes
2answers
3k views

ssh port forward to access my home machine from anywhere

http://serverfault.com/questions/303937/how-to-make-freebsd-box-accessible-from-internet I want to understand this whole process of port forwarding. I read so many things but failing to understand ...
5
votes
3answers
3k views

Moved bin and other folders! How to get them back?

I accidentally moved all folders from root to a subfolder. (/bin, /etc, /home, /lib, /usr... all moved) The only ones that were not moved, since they were in use, are /bak, /boot, /dev, /proc, /sys. ...
26
votes
3answers
2k 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?
16
votes
1answer
2k views

Is there a way in bash to redirect output and still have it go to stdout?

Okay. If I wanted to redirect the output of a program to a file, I'd do something like this prog > file If I wanted to redirect both stdout and stderr to that file, then I'd do prog > file ...
13
votes
1answer
3k views

How can I execute `date` inside of a cron tab job?

I want to create a log file for a cron script that has the current hour in the log file name. This is the command I tried to use: 0 * * * * echo hello >> ~/cron-logs/hourly/test`date "+%d"`.log ...
9
votes
5answers
810 views

Why do I need to quote variable for if, but not for echo?

I've read that you need double quotes for expanding variables, e.g. if [ -n "$test" ]; then echo '$test ok'; else echo '$test null'; fi will work as expected, while if [ -n $test ]; then echo ...
8
votes
5answers
6k views

Remove comma between the quotes only in a comma delimited file

I have a input file delimited with commas (,). There are some fields enclosed in double quotes that are having a comma in them. Here is the sample row 123,"ABC, DEV 23",345,534.202,NAME I need to ...
4
votes
3answers
15k views

Shell Script for logging into a ssh server

I tried writing a shell script which can do automatic login into a ssh server using password which is mentioned in the script. I have written the following code: set timeout 30 /usr/bin/ssh -p 8484 ...
4
votes
3answers
5k views

How do I know that my CPU supports 64bit operating systems under Linux?

How can I find out that my CPU supports 64bit operating systems under Linux, e.g.: Ubuntu, Fedora?
3
votes
2answers
1k views

Installation on debian 5 32-bit without being a root

I am new to Linux and I am trying to install Skype and Google Chrome on my desktop. It runs Debian 5 32-bit. I downloaded the packages from the web but I have no idea how to install them. I have ...
1
vote
2answers
2k views

df says I have 20G more disk space used than du. Why? [duplicate]

I used du to list all folders and sort by size, the results simply doesn't add up to how much disk space is used(using df). There's about 20G in discrepency, why? [root@xxx lib]# du --max-depth=1 -h ...
5
votes
1answer
112 views

How to allow to run su instantly after I added the user to the appropriate group

I have the su executable with the following permissions: bash-4.2# ls -la /bin/su -rws--s--- 1 root wheel 59930 Sep 14 2012 ./su When I am logged in as a user, not in the wheel group and try to ...
5
votes
3answers
325 views

When you type “ls -a”, what is the significance of “.” and “..”?

Whenever you type ls -a into the command prompt, you usually get all of your folders, files, and then you see that the first two entries are . and .. Just curious, but what is the significance of ...
5
votes
1answer
375 views

LoggedFS configuration file syntax

What is the syntax of the LoggedFS configuration file? The official documentation only had usage instructions for the loggedfs command and a configuration file example. Ok, it's XML, but what are ...
58
votes
1answer
60k 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 ...
37
votes
2answers
18k 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 ...
138
votes
22answers
66k views

Repeat a Unix command every x seconds forever

There's a builtin Unix command repeat whose first argument is the number of times to repeat a command, where the command (with any arguments) is specified by the remaining arguments to repeat. For ...
45
votes
4answers
96k 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 ...
55
votes
17answers
5k views

Where should I put software I compile myself?

I need to compile some software on my Fedora machine. Where's the best place to put it so not to interfere with the packaged software?
31
votes
7answers
4k views

Linux tools to treat files as sets and perform set operations on them

Does anyone know of any linux tool specifically designed to treat files as sets and perform set operations on them? Like difference, intersection, etc?
26
votes
9answers
11k views

Correct locking in shell scripts?

Sometimes you have to make sure that only one instance of a shell script is running at the same time. For example a cron job which is executed via crond that does not provide locking on its own (e.g. ...
18
votes
5answers
12k views

Split pages in pdf

I have a scanned pdf file which has scanned two pages on one virtual page (page in pdf file). The resolution is with good quality. The problem is I have to zoom when reading and drag from left to the ...
50
votes
3answers
13k views

Why hard links not allowed to directories in UNIX/Linux

I read in text books that UNIX/Linux doesn't allows hard links to directories but soft links do. Is it because, when we have cycles and if we create hardlinks, and after some time we delete the ...
37
votes
9answers
12k 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 ...
32
votes
3answers
8k views

What is the difference between Halt and Shutdown commands?

What is the difference between the halt and shutdown commands?
19
votes
5answers
10k views

SSH to decrypt encrypted LVM during headless server boot?

When I installed Ubuntu 10.04 and, now, 10.10, I was offered the option of enabling "encrypted LVM" for my hard drive. After choosing that option, I am prompted for my password during boot to decrypt ...
16
votes
1answer
545 views

Configuring, compiling and installing a linux kernel

I'd like to try using a kernel other than the one provided by my distro -- either from somewhere else, or as customized by me. Is this difficult or dangerous? Where do I start?
38
votes
2answers
10k 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 ...
17
votes
2answers
9k views

Do the parent directory's permissions matter when accessing a subdirectory?

If I have a root folder with some restrictive permission, let's say 600, and if the child folders/files have 777 permission will everybody be able to read/write/execute the child file even though the ...
14
votes
2answers
2k views

Measure pipe throughput in the shell

There is a shell command that allows to measure how fast the data goes through it, so you can measure the speed of output of commands in a pipe. So instead of: $ somecommand | anothercommand you ...
12
votes
5answers
28k views

How can I read line by line from a variable in bash?

I have a variable which contains multiline output of a command. What's the most effecient way to read the output line by line from the variable? For example: jobs="$(jobs)" if [ "$jobs" ]; then ...
22
votes
5answers
4k views

Why do hard links exist?

I know what hard links are, but why would I use them? What is the utility of a hard link?
12
votes
5answers
9k views

Show only stderr on screen but write both stdout and stderr to file

How can I use BASH magic to achieve this? I want to only see stderr output on the screen, but I want both stdout and stderr to be written to a file. Clarification: I want both stdout and stderr to ...
10
votes
1answer
3k views

How can I configure a reverse SSH connection to the connecting computer?

I'm going to be deploying a number of machines in the near future which will be behind routers. It won't be feasible to set up dynamic DNS on each router and port forwarding, so is there a way I can ...
8
votes
2answers
10k views

How to install program locally without sudo privileges?

Assume I have ssh access to some Ubuntu server as user and I need some not system tools to be installed for convenience (mc, rtorrent, mcedit). I do not want to bother admins for these small programs. ...
7
votes
5answers
8k views

How to create a DEB file manually?

I want to create a DEB file manually. I would like to just provide a folder which contains data to install, and a script to be executed after installation. Is this possible?

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