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.

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13
votes
3answers
12k views

What is the purpose of -e in sed command?

I can't find any documentation about the sed -e switch, for simple replace, do I need it? e.g. sed 's/foo/bar/' VS sed -e 's/foo/bar/'
13
votes
3answers
8k views

How to safely replace a not-yet-failed disk in a Linux RAID5 array?

I have a software RAID5 array (Linux md) on 4 disks. I would like to replace one of the disks with a new one, without putting the array in a degraded state, and if possible, online. How would that ...
9
votes
3answers
38k views

Format of /etc/hosts on Linux (different from Windows?)

Pasted below this question is a sample of a /etc/hosts file from a Linux (CentOS) and a Windows machine. The Linux file has two tabbed entries after the IP address (that is localhost.localdomain ...
9
votes
4answers
12k views

Finding a substring in files across subdirectories with a single built-in command?

In Windows, if I wanted to find a string across all files in all subdirectories, I would do something like findstr /C:"the string" /S *.h However, in Linux (say, Ubuntu) I have found no other way ...
7
votes
1answer
6k views

How to get Oracle java 7 to work with setcap cap_net_bind_service+ep

I am trying to grant the java executable the right to open ports below 1024 on Linux. Here is the setup /home/test/java contains the Oracle Server JRE 7.0.25 CentOS 6.4 Here is what getcap ...
6
votes
2answers
5k views

How do I share internet with Windows from my Linux box?

I have a Linux (Ubuntu 12.04) PC connected to the internet with a Greenpacket WiMax USB modem. I want to share the Internet connection with another computer running Windows 7 Home Premium, connected ...
6
votes
2answers
9k views

iptables port-mirroring

I need to be able to get a copy of packets received on port 8001 to port 8002. I have tried the following but I get an error that --tee is undefined. sudo iptables -t nat -A PREROUTING -p TCP -s 127....
5
votes
4answers
27k views

Linux file access monitoring

Is there any way in unix to find out who accessed certain file in last 1 week? It may be user or some script ftp it to some other place. Can I get a list of user name who accessed certain file? How ...
15
votes
2answers
1k views

Is it possible to run pure GNU?

On the GNU Project webpage, there's a subsection called "All GNU packages" which lists the various software in the GNU project. Are there any GNU distributions which use only these packages -- i.e. a ...
12
votes
2answers
4k views

Adjusting keyboard sensitivity in a command line terminal?

When using a tty login shell by entering Ctrl-Alt-F1 from an Ubuntu 12.04 install on a laptop the keyboard seems overly sensitive and if my finger lingers for a moment on a button I end up with ...
12
votes
3answers
14k views

ps: full command is too long

Good day! I use 'ps' to see command that starts process. The issue is that command is too long and 'ps' does not show it entirely. Example: I use command 'ps -p 2755 | less' and have following ...
12
votes
3answers
3k views

Creating formatted partition from nothing

I need to create filesystem with just one partition from nothing (/dev/zero). I tried this sequence of commands: dd if=/dev/zero of=mountedImage.img bs=512 count=131072 fdisk mountedImage.img n ...
10
votes
1answer
4k views

How to remove duplicate lines in a large multi-GB textfile?

My question is similar to this question but with a couple of different constraints: I have a large \n delimited wordlist -- one word per line. Size of files range from 2GB to as large as 10GB. I ...
10
votes
2answers
645 views

Triggering an action when a specific volume is connected

I have a USB key that contains my keepass2 password database and I'd like to perform some actions when it is plugged into my computer, namely: Auto-mount it to some specific location When the ...
9
votes
1answer
7k views

Find which files are affected by bad blocks on ext4 filesystem

I have an ext4 filesystem that recently developed some bad sectors. Running fsck.ext4 -c finds and remembers the bad blocks. How can I find which files (if any) included these bad blocks so I can ...
9
votes
1answer
1k views

What's the progress regarding improving system performance/responsiveness during high disk I/O?

Whenever there is high disk I/O, the system tends to be much slower and less responsive than usual. What's the progress on Linux kernel regarding this? Is this problem actively being worked on?
4
votes
1answer
284 views

Shared library mappings in /proc/pid/maps

Why does /proc/pid/maps contain a few records for the same library ? Here is an example: 7fae7db9f000-7fae7dc8f000 r-xp 00000000 08:05 536861 /usr/lib/x86_64-linux-gnu/libstdc++....
3
votes
6answers
2k views

When does a shell get executed during the linux startup process

I do not understand when does a shell, lets say bash, get executed, which program runs bash initially first.
32
votes
1answer
20k views

Linux: What is a tainted kernel?

Under certain conditions, the Linux kernel may become tainted. For example, loading a proprietary video driver into the kernel taints the kernel. This condition may be visible in system logs, kernel ...
19
votes
4answers
10k views

Binary compatibility between Mac OS X and Linux

Brace yourselves, this question will likely appear naive and/or foolish, seeing as I am relatively new to the inner workings of unix like systems, and programming in general. Ready? Ok! I will go ...
14
votes
6answers
1k views

Showing only “interesting” mount points / filtering non interesting types

I used mount to show mounted drives, I don't want to see the not so interesting ones (i.e. non-physical). So I used to have a script mnt that did: mount | grep -Ev 'type (proc|sysfs|tmpfs|devpts) ' ...
13
votes
1answer
7k views

What does a dot after the file permission bits mean?

I performed an ls -la on directory on my CentOS 6.4 server here and the permissions for a given file came out as: -rwxr-xr-x. I understand what -rwxr-xr-x means, what I don't understand is the . ...
8
votes
3answers
649 views

Open Source router firmware options?

What distro's exist that are designed for routers? Please include the following link to the project page link to supported hardware list what distinguishes them, why pick this option friendly web ...
7
votes
4answers
12k 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: ...
6
votes
1answer
3k views

Does kernel: EDAC MC0: UE page 0x0 point to bad memory, a driver, or something else?

kernel: EDAC MC0: UE page 0x0, offset 0x0, grain 0, row 7, labels ":": i3200 UE All of a sudden today, our CentOS release 6.4 (Final) system started throwing EDAC errors. I rebooted, and the errors ...
5
votes
2answers
140 views

Better method for acting on IP address change from the ISP?

I have a Debian server at home. The server is my router and provides VPN access to the outside. I do not have a static IP address; the lease time given by the ISP is two hours.This cable cell seems ...
5
votes
1answer
2k views

I don't want other users see my processes in ps aux. I have root. It's Debian. How to use grsec?

I installed 'linux-patch-grsecurity2' and it has some sort of interface. ~$ sudo gradm2 gradm 2.1.14 grsecurity administration program Usage: gradm [option] ... Examples: gradm -P ...
5
votes
1answer
1k views

Tracking huge buffer usage under Linux

I have a Linux server running under Debian Lenny with 4Go of RAM. It doesn't run much, just: Postfix/spamassassin (daemon mode) Bind9 KVM (one guest - 1Go of RAM for it) Every day at exactly 3:05 ...
4
votes
3answers
1k views

Are there any ways or tools to dump the memory cache and buffer?

As the title, I want to check out what files are loaded in buffer. Just so it's clear, the buffers & cache I'm referring to are what show up when you run the free -m command: $ free -m ...
3
votes
2answers
1k views

How to change environment variables without re-logging to UI?

How can I change environment variables without re-logging to UI? I want to re/define some variables and want them set on my current logged in shell (including UI). I know logging out and then logging ...
9
votes
2answers
4k views

Why does top report the incorrect CPU usage?

I have a machine with Intel(R) Xeon(R) CPU E5520 visible as 16 logical cores (8 with HT). If I run something to eat CPU time (single threaded) top correctly reports 100% CPU usage for the process but ...
9
votes
3answers
22k views

Automating textual input from a bash script without using EOF

I'm running Ubuntu Linux. Suppose there is a program called myprogram. This program prompts the user for input; specifically, the user must type an integer when prompted and press Enter. I would ...
8
votes
2answers
756 views

Cleaner way to delete files on Linux which include a datestamp as part of file name

I have a new requirement to purge MySQL dump files that are older than 30 days. The files use a naming convention of "all-mysql-YYYYMMDD-HHMM.dump". The files are located on SAN mounted file system, ...
7
votes
4answers
3k views

What are the advantages of the Unix file system structure

If I install an application in Linux for example Debian/Gnu Linux, the files of the applications are copied to many different directories in the file system. Some scripts goes into /usr/share .. /usr/...
7
votes
3answers
4k views

How to map ataX.0 identifiers in kern.log error messages to actual /dev/sdY devices?

Consider following kern.log snippet: ata4.00: failed command: WRITE FPDMA QUEUED ata4.00: cmd 61/00:78:40:1e:6c/04:00:f0:00:00/40 tag 15 ncq 524288 out res 41/04:00:00:00:00/04:00:00:00:00/...
6
votes
3answers
8k views

Why is the 'sudo' password different than the 'su root' password

On my personal machine, I often type sudo in front of certain commands in order to accomplish administrative tasks. I had hoped to avoid doing this throughout the day, by typing su root and providing ...
5
votes
2answers
2k views

How to parallelize dd?

I'm currently having trouble with dd invoked with a sparse file as input (if) and a file as output (of) with conv=sparse. dd seems to be using one core of the CPU (Intel(R) Core(TM) i7-3632QM CPU @ 2....
4
votes
2answers
3k views

256 color in Linux console

I have in my .bashrc export TERM=xterm-256color but this cause blinking all colored text (ls --color, in vim etc.) in a Linux console (Ctrl+Alt+F1). So is there any possibility to recognize in ...
4
votes
2answers
2k views

Remapping caps-lock to escape, and menu to compose, on the linux console

When running X I use a .xmodmaprc to remap certain keys thusly: ! Make it so that both Caps Lock and Escape do Escape clear Lock keysym Caps_Lock = Escape ! Remap the menu key as Compose keysym Menu =...
3
votes
1answer
2k views

Fedora's command-not-found doesn't work

I've recently installed Fedora 19. Packagekit-command-not-found is installed. But its own examples don't work. When I enter gedti the output is: bash: gedti: command not found... Similar command is: '...
3
votes
1answer
448 views

Obtaining information about system hardware

If I want to accurately save information about the hardware I am using as a reference, what is the best way to do it? Are the contents of /proc/meminfo sufficient?
11
votes
2answers
1k views

How does the /proc/<pid>/exe symlink differ from ordinary symlinks?

If I start a process and then delete the binary of it, I can still recover it from /proc/<pid>/exe: $ cp `which sleep` . $ ./sleep 10m & [1] 13728 $ rm sleep $ readlink /proc/13728/exe ...
7
votes
2answers
860 views

How to disable system beep for non-privileged user

How to disable system beep on Linux? I don't have superuser powers so I cannot recompile kernel/unload module.
6
votes
2answers
4k views

Edid information

I want to gather the Edid information of the monitor. I can get it from the xorg.0.log file when I run X with the -logverbose option. But the problem is that If I switch the monitor (unplug the ...
5
votes
4answers
899 views

Why does sed act differently depending on the output file?

If I run: cat messages.txt | sed -e 's/a/a/g' > messages.txt on one large file (2500+ lines) I find that the resulting file will only have about 900 lines after the command in cygwin and will ...
5
votes
3answers
12k views

RHEL: Creating stable names for network interfaces

We have a RHEL 5.5 box with 8 interfaces. And the eth interface naming is flip flopping. Sometimes eth0 comes up on physical port 7th, and sometimes on another physical port. We want the naming to ...
4
votes
2answers
2k views

Linux Mint: drives' map changing at reboot brings fstab error

I've set up fstab to auto mount media drives on a Linux Mint machine. The OS is installed on a IDE/ATA Disk while 3 SATA disks hold data to share. The BIOS has the ATA disk as first boot device. All ...
4
votes
5answers
1k views

Multiple terminals at once without an X server

There is a way to visualize multiple terminals at the same time without running a Xorg session ? I have a really low profile machine that could be great for some basic stuff but has an horrible ...
4
votes
2answers
7k views

Disable direct login for normal users (like oracle) in linux but allow scp and sftp?

Is it possible to disable direct login for normal users (like oracle) in linux but allow scp and sftp for that use?
3
votes
1answer
2k views

tty (console): disable monitor

In .xinitrc, I use xrandr --output LVDS1 --off to disable the monitor of my laptop (I always use a projector at school). But, before I log in with xinit, or when I temporary go to the console (...