Bash is the Bourne Again SHell, the successor to the classic Unix sh (shell).

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37
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7answers
30k views

Log all commands run by admins on production servers

It is company policy for admins to login to the servers via a personal username, and then run sudo -i to become root. Upon running sudo -i, sudo will create an environmental variable called SUDO_USER,...
16
votes
7answers
23k views

How can I determine what is taking up so much space? [duplicate]

I was using df -h to print out human readable disk usage. I would like to figure out what is taking up so much space. For instance, is there a way to pipe this command so that it prints out files that ...
445
votes
34answers
215k views

How can I sort du -h output by size

I need to get a list of human readable du output. However, du does not have a "sort by size" option, and piping to sort doesn't work with the human readable flag. For example, running: du | sort -...
142
votes
39answers
78k views

What useful things can one add to one's .bashrc? [closed]

Is there anything that you can't live without and will make my life SO much easier? Here are some that I use ('diskspace' & 'folders' are particularly handy). # some more ls aliases alias ll='ls -...
124
votes
9answers
71k views

Keeping a linux process running after I logout

I'm connecting to a Linux machine through SSH, and I'm trying to run a heavy bash script that makes filesystem operations. It's expected to keep running for hours, but I cannot leave the SSH session ...
14
votes
4answers
6k views

Do background processes get a SIGHUP when logging off?

This is a followup to this question. I've run some more tests; looks like it really doesn't matter if this is done at the physical console or via SSH, neither does this happen only with SCP; I also ...
6
votes
2answers
4k views

My cron tasks report command not found [duplicate]

This is the contents of my crontab file: 0 0,6,12,18 * * * cd /var/www/app/current && backup perform --trigger db_backup --config_file config/backup.rb --data-path db --log-path log --tmp-...
3
votes
3answers
11k views

Deleting files from Remote FTP-Server older than x days

i've got a remote FTP server where i store some backups via cronjob. The Problem is that i only got a little amount of space so im doing incremental backups. I want to keep the backups about 14 days. ...
412
votes
12answers
511k views

How to determine if a bash variable is empty?

What is the best way to determine if a variable in bash is empty ("")? I have heard that it is recommended that I do if [ "x$variable" = "x" ] Is that the correct way? (there must be something more ...
71
votes
6answers
56k views

How to test if my server is vulnerable to the ShellShock bug?

How can I ensure my Bash installation is not vulnerable to the ShellShock bug anymore after the updates?
29
votes
5answers
2k views

Avoid to keep command in history

I use bash and I would like to avoid some commands being kept in the history. Is it possible to do that for the next command only? Is it possible to do that for the entire session?
28
votes
5answers
52k views

How to get pid of just started process

I want to start process (eg. myCommand) and get its pid (to allow to kill it later). I tried ps and filter by name, but I can not distinguish process by names myCommand ps ux | awk '/<myCommand&...
15
votes
2answers
13k views

What is the difference between sudo -i and sudo su -

What is the difference between commands sudo -i and sudo su -? Are they the same?
7
votes
2answers
10k views

how to filter rsyslog messages by tags

I have several applications and scripts that I want to redirect the output to custom files. I launch those applications using command | logger -t TAG I would like to filter these messages based ...
5
votes
2answers
9k views

No TTY present when running commands over SSH in here-document

I'm trying to run a command over SSH like this in a here-document: ssh example.com <<END sudo /etc/init.d/apache2 reload END Which normally works except when I'm trying to run something that ...
4
votes
4answers
6k views

How can I display the IP address of an interface?

If I want to display the IP address that is assigned to eth1, how can I do this in Bash?
3
votes
5answers
946 views

Difference of running scripts manually or with a cronjob

I have a PHP script that I want to run every 10 minutes, going through database records and creating/editing movies through MEncoder. I've set up cron job to accomplish this, but it doesn't work very ...
1
vote
3answers
2k views

Bash piping answer in Ubuntu

In a bash script, I want to know know how to pipe in answers like for example: ssh -l username -i /home/ubuntu/.ssh/id host.com < yes The ssh connection would ask if I would like to continue the ...
111
votes
85answers
16k views

Linux command line best practices and tips?

I would like to open a discussion that would accumulate your Linux command line (CLI) best practices and tips. I've searched for such a discussion to share the below comment but haven't found one, ...
192
votes
5answers
75k views

What is the difference between double and single square brackets in bash?

I just wondered what exactly the difference between [[ $STRING != foo ]] and [ $STRING != foo ] is, apart from that the latter is posix-compliant, found in sh and the former is an extension ...
22
votes
6answers
20k views

If I launch a background process and then log out, will it continue to run?

Asking this after a prolonged discussion with a coworker, I'd really like a clarification here. I launch a background process, either by appending "&" to the command line or by stopping it with ...
31
votes
6answers
286k views

How to pass password to scp command used in bash script? [duplicate]

Possible Duplicate: Connect through SSH and type in password automatically, without using a public key I have a bash script that makes dump of DB then copies file from one server to another ...
11
votes
2answers
17k views

Writing to stdin of background process

I'm on an Ubuntu 10.04 box, and started a server in the background (myserver &) over ssh. It's been running fine, but I need a way to get at the server's stdin, as the only way to control the ...
10
votes
3answers
4k views

Logging a “persons” activity in Linux

So I've read many of the posts related to this and have just come up more confused than before. There are recommendations for various tools including ttyrec, snoopy, acct, rootsh, sudosh, ttyrpld, ...
30
votes
3answers
5k views

In Bash, are wildcard expansions guaranteed to be in order?

Is the expansion of a wildcard in Bash guaranteed to be in alphabetical order? I am forced to split a large file into 10 Mb pieces so that they can be be accepted by my Mercurial repository. So I was ...
11
votes
7answers
45k views

script to automatically test if a web site is available

I'm a lone web developer with my own Centos VPS hosting a few small web sites for my clients. Today I discovered my httpd service had stopped (for no apparent reason - but that's another thread). I ...
17
votes
2answers
14k views

How to repeatedly call rsync until files are sucessfully transferred

I'm trying to syncronize files from a remote server that is not reliable, meaning the connection tends to fail "randomly" with rsync: connection unexpectedly closed Rsync is called with --...
16
votes
6answers
53k views

Determine if filesystem or partition is mounted RO or RW via Bash Script?

Is there an easy way to determine if a mounted filesystem is mounted as Read-Only or Read-Write? I was thinking just to pipe mount but I thought there might be an easier way.
12
votes
3answers
11k views

Rsync seems incompatible with .bashrc (causes “is your shell clean?”)

It turns out rsync can't work with a remote server which has a .bashrc file? At local client i got when run rsync: protocol version mismatch -- is your shell clean? (see the rsync man page for an ...
9
votes
4answers
20k views

kill a screen (but not all screens)

I have multiple screens running on an Ubuntu server that are initiated as: screen -dmS screen1 cmd screen -dmS screen2 cmd etc... And I need to kill one screen, but not all of them. What is the ...
9
votes
2answers
11k views

How to keep: daily backups for a week, weekly for a month, monthly for a year, and yearly after that

I need to backup data and config files on this server, daily. I need to keep: daily backups for a week weekly backups for a month monthly backups for a year yearly backups after that All of this ...
5
votes
3answers
8k views

Escaping spaces in a remote path when using rsync over a remote SSH connection

When using SSH to connect rsync to a remote server, how do you escape spaces and such in the remote path? A simple backslash escapes the space for the local bash prompt, but on the remote machine the ...
23
votes
6answers
9k views

What does passing the -xe parameters to /bin/bash do

Exactly what the title says. I'm not having much luck finding the proper documentation to see what -xe does in the following use case: #!/bin/bash -xe what do those parameters do and where it is ...
10
votes
4answers
11k views

Why does the $PATH of an ssh remote command differ from that of an interactive shell?

I have a user that has made no modifications to the $PATH in any dot-files: it is exactly the system default setting. From a login shell: $ ssh example.com user@example.com:~$ cat /tmp/hello.hs #!/...
9
votes
1answer
798 views

Is it possible to hide a malicious alias in Bash on Linux?

Is it possible to conceal the existence of a malicious alias in Bash on a Linux system and have it executed by the user without their knowledge?
5
votes
2answers
7k views

ssh fails to execute remote command when run from cron bash script - works from CLI

I have a script, written in bash, which runs from cron. One of the first things it does is SSH to a remote host and retrieve a list of files in a directory. Everything works fine when run from the ...
2
votes
3answers
7k views

“Corrupted MAC on input. Packet Corrupt” on file transfer over SSH, SCP, and FTP on Linux Server

help on this would be great. Specs: LAMP server Linux OS - Debian 5.0.1 4x Intel(R) Xeon(TM) CPU 2.80GHz Important Packages: openssl - SSL security iptables - firewall to block all requests ...
18
votes
1answer
2k views

Shell command slow when using pipe, fast with intermediate file

Does anyone understand this huge difference in processing time, when using an intermediate file, or when using a pipe? I'm converting tiff to pdf using standard tools on a fresh debian squeeze server. ...
7
votes
4answers
14k views

In unix, what's the best way to reduce the size of a massive log file that is actively being written to?

On a linux server, I want to reduce the size of a log file which is several GB big. Cutting off the top half, or maybe the first million lines would work.
5
votes
3answers
7k views

Bash prompt on Ubuntu - FQDN (\H) same as hostname (\h)

We've got seperate environments at my workplace for development, testing, integration, and staging. Within those envs, we've overloaded the hostnames in DNS - e.g. in the dev environment, the primary ...
16
votes
1answer
794 views

can't type lower cased e in amazon ec2 (Amazon Linux)

After a few days of operation on my new ec2 build, the following happens: I log into SSH, everything is fine, I do my coding I return the next day, and log into SSH I cannot type a lower cased e ...
5
votes
2answers
1k views

How can I make bash to log shell commands to syslog?

Bash 4.1 is able to log the history to syslog. However I can't seem to make it work under FreeBSD 8. I've tried re-compiling bash from ports with -DWITH_SYSLOG= but to no avail. Has anyone managed to ...
5
votes
4answers
3k views

less with “update file” like functionality

I want to watch a file that gets overwritten every 5 minutes with less. How can I make less follow the new file descriptor instead of keeping the old one displayed? watch "cat file" won't do it ...
3
votes
1answer
1k views

How to detect, in the guest operating system, if the vmware tools are out of date?

I'm trying to find a generic way of checking, in the guest operating system of a virtual machine, if the VMware Tools are out of date. The best way I have found so far has been to check the output of ...
2
votes
4answers
268 views

List all empty folders

I have a bunch of nested folders. Most folders contain files. Some contain hundreds of thousands of files. Some are empty. I want to get a list of all empty folders. However, when I run: find -...
0
votes
2answers
290 views

bash stuck at 3.2-24.el5 (Redhat)

I'm trying to update bash on our Red Hat Enterprise Linux Server release 5.6 server. But it won't find an update later than "3.2-24.el5". I've check and it is vulnerable for the shellshock ...
6
votes
4answers
11k views

Is it possible to run a command on windows server from Linux?

I want to restore a sqlserver db backup on remote windows server from linux. I tired "net rpc" but there is nothing for execute a command or script on remote server.
4
votes
2answers
270 views

Repartitioning two disks without a loss of data

I am interning at a software company and I have hit somewhat of a brick wall. Here is the deal: The Problem: We have some boxes around here that were incorrectly partitioned for 2 x 500 GB drives. ...
2
votes
1answer
654 views

Binary won't execute when run with a path. Eg >./program won't work but >program works fine

I'm getting some weird behaviour for a binary file I'm trying to run. I'm using Mac OSX snow leopard, and the binary itself is part of labkey software .. built from source. If I try to run the file ...
1
vote
1answer
121 views

Disconnect modem when postfix queue empty

in /etc/ppp/ip-up.d/script I have the following that runs fetchmail when the ppp0 interface is up (connected) and when it finish the modem ends internet conection automatically. #!/bin/sh /usr/bin/...