All Questions
26,140
questions
16
votes
3
answers
26k
views
cp --no-target-directory explained
Question: I need a simple example of how to use cp --no-target-directory.
I do experience some difficulties in understanding cp --no-target-directory. I do understand the explanation for mv --no-...
- 5,040
16
votes
3
answers
27k
views
How do I remove all files in a folder except just some specified files?
I want to remove all files in a directory while leaving just some specified files, they don't have anything in common by name. How could I achieve that?
For example, the file names I want to keep are:...
- 7,605
16
votes
2
answers
35k
views
How to tell rsyslog to create log file if not there?
Default behaviour by rsyslog is to append traces to an existing log file.
Now, I've seen (CentOs, Scientific Linux) that when rsyslog is already running, you delete the log file (e.g. the one ...
- 5,035
16
votes
1
answer
38k
views
Move free space from end of the drive to first partition with gparted
I am in a frustrating situation - no matter how I try, gparted won't let me assign the empty space to the first partition:
The middle partition is blocking me from expanding /dev/sda1. I need to move ...
- 1,776
16
votes
3
answers
2k
views
Bash, always check $PWD as part of path?
Background: One of my colleagues who doesn't come from a Linux background asked me about using ./ before some commands and not others, so I explained to him how PATH works and how binaries are chosen ...
- 263
16
votes
6
answers
13k
views
Find recursively all archive files of diverse archive formats and search them for file name patterns
At best I would like to have a call like this:
$searchtool /path/to/search/ -contained-file-name "*vacation*jpg"
... so that this tool
does a recursive scan of the given path
takes all files with ...
- 271
16
votes
2
answers
22k
views
How to pass a passphrase to ssh-add without triggering a prompt?
I read man ssh-add and I don't see a flag for passing a passphrase like we have in ssh which is -p.
I tried
# the -K is for macOS's ssh-add but it's not relevant
ssh-add -q -K ~/.ssh/id_rsa <<&...
16
votes
3
answers
8k
views
How can I instruct BSD sed to interpret escape sequences like \n and \t?
I have a sed replacement command that I would like to be compatible with BSD sed as well as GNU sed. Extended regular expressions are not an issue as I do not need them in this case. My primary ...
- 1,006
16
votes
2
answers
25k
views
Why is $1 in a function not printing the script's first argument?
Why doesn't echo $1 print $1 in this simple bash script?
#!/bin/bash
# function.sh
print_something () {
echo $1
}
print_something
$ ./function.sh 123 -> why doesn't it print '123' as a result?
- 429
16
votes
6
answers
4k
views
Utility to buffer an unbounded amount of data in a pipeline?
Is there a utility that I can stick in a pipeline to decouple read and write speeds?
$ producer | buf | consumer
Basically, I want a utility buf that reads its input as fast as possible, storing it ...
- 671
16
votes
2
answers
30k
views
Under what conditions exactly does SIGPIPE happen?
Say we have a named pipe called fifo, and we're reading and writing to it from two different shells. Consider these two examples:
shell 1$ echo foo > fifo
<hangs>
shell 2$ cat fifo
foo
shell ...
- 272
16
votes
4
answers
79k
views
Terminal, Prompt changed to "-Bash-4.2" and colors lost
Usually my terminal prompt was
username place$
now it only shows
bash-4.2$
and all the color settings have been lost (on the terminal profile I have the same color scheme, but it just don't show ...
- 263
16
votes
3
answers
25k
views
Using in/out named pipes for a TCP connection
I've been fiddling with getting this to work for a while now, so I suspect some sort of fundamental misunderstanding about how pipes work is the root cause of my troubles.
My goal is to initiate a ...
- 1,140
16
votes
2
answers
44k
views
How to clean up bootloaders & UEFI entries from other installs?
I got a new Windows laptop, and I wanted to dual boot with Linux. I installed Fedora, before changing my mind and going back to Mint. I'd like to keep Win 8.1 and Mint.
However, now my UEFI boot menu ...
- 261
16
votes
2
answers
12k
views
What is the rationale behind EINTR?
Small talk as background
EINTR is the error which so-called interruptible system calls may return. If a signal occurs while a system call is running, that signal is not ignored. If a signal handler ...
- 905
16
votes
8
answers
44k
views
sed - remove the very last occurrence of a string (a comma) in a file?
I have a very large csv file. How would you remove the very last , with sed (or similar) ?
...
[11911,0,"BUILDER","2014-10-15","BUILDER",0,0],
[11912,0,"BUILDER","2014-10-15","BUILDER",0,0],
[11913,...
- 18.1k
16
votes
1
answer
63k
views
Start a background process from a script and manage it when the script ends
I'd like to run and configure a process similarly to a daemon from a script.
My shell is zsh emulated under Cygwin and the daemon is SFK, a basic FTP server.
For what matters here, the script ...
- 1,453
16
votes
3
answers
33k
views
rpc.statd running on system not using NFS
I have a Debian machine that gets warnings (via the Tiger automatic auditor) that rcp.statd is listening on such-and-such socket. Googling shows rpc.statd is a daemon used by NFS. As far as I know, I'...
- 860
16
votes
3
answers
3k
views
Count nul delimited items in file
I have a shell script which uses find -print0 to save a list of files to be processed into a temporary file. As part of the logging I'd like to output the number of files found, and so I need a way ...
- 2,588
16
votes
5
answers
19k
views
Special File that causes I/O error
I want to automatically test if a piece of software reacts as expected if an essential SQLite DB file fails to be read (causing an I/O error). Exactly that happened some days ago at a client. We ...
- 3,583
16
votes
2
answers
40k
views
How can I completely reinstall mysql?
I had to reboot in the middle of a large data import. I only have one mysql database, which has now been corrupted.
How can I completely remove mysql and reinstall it? I've tried apt-get purge mysql-...
- 45.4k
16
votes
1
answer
11k
views
Why do these bash fork bombs work differently and what is the significance of & in it?
I get how a normal fork bomb works, but I don't really understand why the & at the end of the common bash fork bomb is required and why these scripts behave differently:
:(){ (:) | (:) }; :
and
...
- 163
16
votes
2
answers
9k
views
Cannot execute binary in NixOS - No such file or directory
I tried to install the current oracle jre on a VM running NixOS.
Now the following happens:
[michas@cc:~]$ tar xvzf jre-7u40-linux-x64.tar.gz |grep bin/java
jre1.7.0_40/bin/javaws
jre1.7.0_40/bin/...
- 21.5k
16
votes
4
answers
18k
views
Adding paths to PATH using a multi-line syntax
As far as I understand, the usual way to add a path to the PATH environment variable is by concatenating paths separated by the : character.
For example, if I want to add three paths to it /my/path/...
- 41.2k
16
votes
3
answers
8k
views
Can I limit a process to a certain amount of time / CPU cycles?
We have a script which runs on our web servers, triggered by customer action, which initiates a unix process to generate some cache files. Because this process acts upon files supplied by our customer,...
- 8,458
16
votes
4
answers
18k
views
Can I setup a loopback audio device?
If I can send audio to the output devices, then I can record the same audio as a wave. With filesystems, you can just setup a loopback filesystem and write binary data on a file instead of a device.
...
- 1,576
16
votes
2
answers
8k
views
Why are there so many virtual terminal devices?
I've been reading the Advanced Linux Programming book and it mentions about virtual terminals which, if I understood it correctly, it is a Linux-specific feature (not in Unix) to allow multiple login ...
- 325
16
votes
7
answers
10k
views
Remove trailing new line from 'clipboard' to prevent execution on the terminal?
Is there some way to run whatever you copy to the 'clipboard' through some sort of filter? Ideally to strip out the trailing newline from something you copy, so that it doesn't auto-run in the ...
- 1,774
16
votes
2
answers
36k
views
Is halt the same as "shutdown -H" and poweroff the same as "shutdown -P"?
I haven't found a clear answer to the differences between the two options to the command shutdown.
Is halt the same as shutdown -H and poweroff the same as shutdown -P?
- 102k
16
votes
3
answers
41k
views
ssh remote server on some port other than 22 without password
I am usually connecting to the remote server with
ssh [email protected] -p 11000
and then giving the password each time for user.
How should I avoid entering the password each time I connect using ...
- 263
16
votes
2
answers
14k
views
Get directory from which script was called from
I have a script doSmth in /usr/bin. Is it possible to get and print the directory the script was called from?
So if I call doSmth from /home/me the output will be /home/me.
- 905
16
votes
1
answer
7k
views
background process pipe-input
if i want to display "aaa" on screen:
(1)$: echo aaa | cat ... works OK
(2)$: echo aaa | ( cat ) ... works OK
(3)$: echo aaa | ( cat & ) ... NOT working
(4)$:...
- 1,731
16
votes
3
answers
92k
views
How can I cd into a directory as root?
Let's say there's a directory that I don't have the privileges to access. Obviously sudo cd foo won't work, because cd is a shell builtin in every shell ever.
So far, I've just been using sudo bash (...
- 15k
16
votes
5
answers
8k
views
How can I find out which files are lost through a ddrescue recovery atempt?
I am in the process of salvaging data from a 1 TB failing drive (asked about it in Procedure to replace a hard disk?). I have done ddrescue from a system rescue USB with a resulting error size of ...
- 303
16
votes
2
answers
8k
views
Detach/reattach an application run on X over SSH?
I have a development server that I leave running all the time, and a development laptop that I turn off/on everyday.
I have a GUI application on the server that I'd like to run over SSH -X, and I'd ...
- 285
16
votes
6
answers
27k
views
Unlock LUKS encrypted Debian root with key file on boot partition
I'm trying to decrypt the Debian root with a key file stored in the boot partition (decrypted partition). This will break the security, but it doesn't matter now. I have to conclude this successfully ...
- 161
16
votes
3
answers
22k
views
Split file into multiple small files, separate by the newline symbol
Is there a utility that split file by newline symbol? e.g if a file contains the following lines,
aa
bbb
cccc
If I want to split it to 3 files, the desired output would be:
aa, bbb And cccc (in 3 ...
- 54.6k
16
votes
2
answers
65k
views
Create and control start up scripts in BusyBox
I have compiled a custom linux kernel in BusyBox. BusyBox init does not support runlevels. When the kernel boots up in BusyBox, it first executes init which looks for the specified runlevel in /etc/...
16
votes
4
answers
60k
views
Creating a snapshot of a linux system
I want to do the following - Save the current state of my linux OS(centOS6.5). Do some changes (more specifically inject a fault and test some service to check how it behaves when that particular type ...
- 441
16
votes
1
answer
5k
views
Double click selection in Gnome Terminal
Double clicking on a word in gnome terminal selects the whole word. Unfortunately, this selection doesn't include colons such that URLs aren't completely selected, e.g. with
http://foo.example.org/
...
- 57.6k
16
votes
4
answers
54k
views
how to execute a bash script without typing ./ [duplicate]
It has been bugging me for a very long time and I'm really sick of it. For example there's a script called testscript that compares two directories. In class the prof can just type
testscript dir1 ...
- 309
16
votes
2
answers
71k
views
Repairing python setup
On my Kubuntu 14.4 (which has python 2.7.6 as standard) my python is broken after I tried to install python 2.7.10 after building from source from python.org with the help of How to install the latest ...
- 657
16
votes
2
answers
33k
views
reliable return code of background process
Let's assume the following piece of bash code:
foo > logfile 2>&1 &
foo_pid=$!
while ps -p$foo_pid
do
ping -c 1 localhost
done
wait $foo_pid
if [[ $? == 0 ]]
then
echo "foo ...
16
votes
3
answers
20k
views
Creating bootable Debian image with debootstrap
I have been trying to create a bootable debian (jessie/8.4) image for the past 2 days, and as far as I can tell I have the procedure right, but I can not get the filesystem right. I am relatively sure ...
- 351
16
votes
2
answers
29k
views
Why can't root on one machine change nfs mounted content from another machine?
On my NFS server, I have the following export defined:
#NFS exports Database
/shared -alldirs -network=192.168.1 -mask=255.255.255.0
On my NFS client:
192.168.1.7:/shared /shared nfs rw 0 0
...
- 11.8k
16
votes
2
answers
25k
views
Where does grep -r search by default?
I found if I search using grep without specifying a path, like grep -r 'mytext' it takes infinitely long. Meanwhile if I search with path specified grep -r 'mytext' . it instantly finds what I need. ...
user7477
16
votes
1
answer
19k
views
Pacman -Syu fails `/bin exists in filesystem`
I was trying to upgrade my arch linux with pacman -Syu after having returned from vacation and now I get this error that I cannot quite make sense of:
(133/133) checking for file conflicts ...
- 311
16
votes
3
answers
19k
views
How to get rid of desktop environment and use a window manager only?
I have been using xterm for all my work. I realized that the features that desktop environments like GNOME has to provide are not of much use to me. Now, is it possible that I remove GNOME and KDE ...
- 5,783
16
votes
1
answer
28k
views
quotas not linked to users but to directories
Usually, quotas are enforced per user, as related to the proprietary of the file.
Is it possible to apply a quota on a folder basis, in such a way, that a folder contents are limited in disk space?
- 480
16
votes
3
answers
3k
views
What was the reason of the non-preemptivity of older Linux kernels?
Why did the first Linux developers choose to implement a non-preemptive kernel? Is it to save synchronization?
As far as I know, Linux was developed in the early '90s, when PCs had a single processor....
- 161