17
votes
7answers
21k views

Which GUI diff viewer would you recommend, with Copy-to-Left/Right functionality?

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 ...
14
votes
3answers
3k views

Reattach to lost X11 session

I'm using X11 forwarding over ssh to run Linux apps on my Windows box, and when the network drops it loses everything that was running. Is there anything similar to screen for X11?
12
votes
1answer
4k 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 ...
18
votes
3answers
7k 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 ...
12
votes
5answers
11k 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 ...
20
votes
1answer
3k views

What does adduser do that useradd doesn't?

In addition to the more widespread useradd, Debian based systems also contain an additional adduser command which provides a higher level interface for adding users and some related tasks. There are ...
15
votes
5answers
913 views

How to compile and install programs from source

This is an issue that really limits my enjoyment of Linux. If the application isn't on a repository or if it doesn't have an installer script, then I really struggle where and how to install an ...
28
votes
2answers
24k views

How do I do a ls and then sort the results by date created?

In what order are the dated ordered by? Certainly not alphanumeric order. ls -lt sorts by modification time. But I need creation time.
19
votes
5answers
4k views

Why is echo a shell built in command?

$ which echo echo: shell built-in command. $ which ls /bin/ls $ which cat /bin/cat Why is echo not an independent utility like ls, ps, cat etc? Why is it shell specific? Any good reasons?
14
votes
2answers
6k 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 ...
8
votes
1answer
860 views

Why is my bash prompt getting bugged when I browse the history?

Often when I start looking at history of commands some of the characters from a command displayed aren't erased, for example: What's happening: prompt$ some_command prompt$ some_commanother_command ...
32
votes
1answer
4k views

How to do a `tail -f` of log rotated files?

On a long running system I usually have a terminal with $ tail -f /var/log/kern.log or something like this open. But from time to time I have to restart such command because no new messages are ...
21
votes
4answers
3k views

Single dashes `-` for single-character options, but double dashes `--` for words?

Where did the convention of using single dashes for letters and doubles dashes for words come from and why is continued to be used? For example if I type in ls --help, you see: -a, --all ...
14
votes
3answers
6k 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?
11
votes
9answers
1k views

Detect init system using the shell

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 ...
10
votes
2answers
463 views

Order of redirections

I don't quite understand how the computer reads this command. cat file1 file2 1> file.txt 2>&1 If I understand, 2>&1 simply redirect Standard Error to Standard Output. By that ...
6
votes
6answers
597 views

How can I reproduce commands run on one machine on another machine?

I would like to install some software on a linux-machine that I have run in VirtualBox. Then I would like to do the same thing on a linux-VPS. I think that I can save all commands that I run using ...
5
votes
3answers
4k 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. ...
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. ...
8
votes
3answers
220 views

How to define similar bash function at once

I have these functions in ~/.bashrc: function guard() { if [ -e 'Gemfile' ]; then bundle exec guard "$@" else command guard "$@" fi } function rspec() { if [ -e 'Gemfile' ]; ...
8
votes
6answers
8k views

Shell script for moving oldest files?

How do I write a script for moving just the 20 oldest files from one folder to another? Is there a way to grab the oldest files in a folder?
28
votes
3answers
3k 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?
9
votes
5answers
1k 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
3answers
9k 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?
7
votes
3answers
25k 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 ...
5
votes
2answers
504 views

Portability of file descriptor links

I've always wondered this but never took the time to find out, so I'll do so now - how portable is the usage shown here of either /proc/$$/fd/$N or /dev/fd/$N? I understand POSIX guarantees /dev/null, ...
10
votes
1answer
2k views

What does *~ mean?

At the end of a makefile I saw rm -f *~ *.class I understand the *.class, but what's *~?
6
votes
3answers
477 views

Access to original contents of mount point

On my headless NAS I have sdf1 (a flash-card) mounted as / while /home is mounted from lv00 (an LVM volume backed by a software RAID). To be able to access the machine when the RAID fails, I have a ...
2
votes
1answer
1k views

controlling priority of applications using cgroups

I would like to understand cgroups better and would like to understand the use-cases for applying cgroups. Are cgroups a good way for prioritizing different applications (i.e, giving higher priority ...
1
vote
2answers
3k 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
155 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
361 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
449 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 ...
4
votes
2answers
1k views

CP: max source files number arguments for copy utility

Consider that there are countless number of files under /src/ cp /src/* /dst/ How many files cp will successfully process?
4
votes
2answers
412 views

`find` with multiple `-name` and `-exec` executes only the last matches of `-name`

When I'm using find . -type f -name "*.htm*" -o -name "*.js*" -o -name "*.txt" it finds all the types of file. But when I add -exec at the end: find . -type f -name "*.htm*" -o -name "*.js*" -o ...
3
votes
2answers
659 views

SSH tunnel through middleman server - how to connect in one step (using key pair)?

My question is basically how to turn my existing two steps into one step. I have a working SSH tunnel set up between two computers using a middleman server like this: ...
73
votes
1answer
80k 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 ...
58
votes
9answers
4k views

Tips for putting ~ under source control

I want to put my home directory (~) under source control (git, in this case), as I have many setting files (.gitconfig, .gitignore, .emacs, etc.) in there I would like to carry across machines, and ...
162
votes
22answers
91k 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 ...
62
votes
17answers
6k 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?
79
votes
7answers
22k views

Why use swap when there is more than enough free space in RAM?

Using swap space instead of RAM can drastically slow down a PC. So why, when I have more than enough RAM available, does my Linux system (Arch) use the swap? Checkout my conky output below: Also, ...
31
votes
7answers
5k 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?
31
votes
5answers
12k views

How to check if a shell is login/interactive/batch

I think I understand the differences between an interactive, a login and a batch shell. See the following links for more help: What is the difference between a 'Login' and an 'Interactive' bash ...
21
votes
5answers
15k 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 ...
64
votes
5answers
17k 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 ...
47
votes
10answers
19k 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 ...
22
votes
4answers
1k 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 ...
35
votes
3answers
14k views

What is the difference between Halt and Shutdown commands?

What is the difference between the halt and shutdown commands?
37
votes
6answers
15k views

Different linux distros sharing the same /home folder?

What is the best way to share the same /home directories between different linux distribution? I mean, I want to have both, say, Fedora and Arch, and I want to find my files at home no matter which ...
49
votes
3answers
2k views

How do the internals of sudo work?

How does sudo work internally? How is it possible that it can become root without having the root password, unlike su? What syscalls, etc. are involved in the process? Is it not a gaping security hole ...

15 30 50 per page