Greatest Hits
750
votes
8
answers
2.4m
views
How to automate SSH login with password?
How to automate SSH login with password?
I'm configuring my test VM, so heavy security is not considered. SSH chosen for acceptable security with minimal configuration.
ex)
echo password | ssh id@...
- 10.7k
1833
votes
3
answers
2.2m
views
What is a Pem file and how does it differ from other OpenSSL Generated Key File Formats?
I am responsible for maintaining two Debian servers. Every time I have to do anything with security certificates, I Google for tutorials and beat away until it finally works.
However, in my searches ...
- 19.9k
816
votes
18
answers
2.9m
views
Ping a Specific Port
Just a quick sanity check here.
Can you ping a specific port of a machine, and if so, can you provide an example?
I'm looking for something like ping ip address portNum.
- 8,285
1461
votes
39
answers
1.2m
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 -...
- 18.1k
791
votes
9
answers
1.1m
views
Can scp copy directories recursively?
Currently I can only copy a single .tar file. But how can I copy directories recursively with scp?
- 8,671
1018
votes
15
answers
1.4m
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 ...
- 23.3k
2494
votes
31
answers
555k
views
Our security auditor is an idiot. How do I give him the information he wants?
A security auditor for our servers has demanded the following within two weeks:
A list of current usernames and plain-text passwords for all user accounts on all servers
A list of all password ...
user80776
558
votes
33
answers
1.2m
views
How do I tell Git for Windows where to find my private RSA key?
My Git setup runs fine on Linux, but when I try to set things up under Windows (using Git for Windows and TortoiseGit), I don't know where to put my private SSH key (or, better still, how to tell ssh ...
- 6,051
481
votes
5
answers
1.2m
views
What's the default superuser username/password for postgres after a new install?
I have just installed postgres 8.4 on Ubuntu 9.10 and it has never asked me to create a superuser. Is there a default superuser and its password? If not, how do I create a new one?
- 6,321
157
votes
9
answers
1.3m
views
Command line to list users in a Windows Active Directory group?
Is there a command line way to list all the users in a particular Active Directory group?
I can see who is in the group by going to Manage Computer --> Local User / Groups --> Groups and double ...
Flyer
342
votes
5
answers
909k
views
How to send ctrl+alt+del using Remote Desktop?
How can I send ctrl+alt+del to a remote computer over Remote Desktop?
For example, if I wanted to change the local admin password on a remote PC using a Remote Desktop connection, it would be helpful ...
- 3,523
503
votes
23
answers
360k
views
mysqldump throws: Unknown table 'COLUMN_STATISTICS' in information_schema (1109)
Every time I try to make a mysqldump I get the following error:
$> mysqldump --single-transaction --host host -u user -p db > db.sql
mysqldump: Couldn't execute 'SELECT COLUMN_NAME, ...
- 6,419
569
votes
6
answers
499k
views
ssh returns "Bad owner or permissions on ~/.ssh/config"
When I try to ssh to another box, I get this strange error
$ ssh hostname
Bad owner or permissions on ~/.ssh/config
But I made sure that I own and have rw permissions on the file:
ls -la ~/.ssh/
...
- 14.7k
84
votes
16
answers
697k
views
What causes SSH error: kex_exchange_identification: Connection closed by remote host?
I setup a SSH server online that is publicly accessible by anyone. Therefore, I get a lot of connections from IPs all over the world. Weirdly, none actually try to authenticate to open a session.
I ...
- 942
259
votes
5
answers
1.4m
views
Can you pass user/pass for HTTP Basic Authentication in URL parameters?
I believe this is not possible, but someone I know insisted that it works. I don't even know what parameters to try, and I haven't found this documented anywhere.
I tried http://myserver.com/~user=...
- 6,050
642
votes
18
answers
944k
views
How do you find what process is holding a file open in Windows?
One thing that annoys me no end about Windows is the old sharing violation error. Often you can't identify what's holding it open. Usually it's just an editor or explorer just pointing to a relevant ...
- 10.1k
308
votes
8
answers
1.4m
views
Check if port is open or closed on a Linux server?
How can I check if a port is listening on a Linux server?
- 3,247
394
votes
27
answers
479k
views
How can I get the size of an Amazon S3 bucket?
I'd like to graph the size (in bytes, and # of items) of an Amazon S3 bucket and am looking for an efficient way to get the data.
The s3cmd tools provide a way to get the total file size using s3cmd ...
- 4,395
191
votes
9
answers
1.2m
views
Resolve host name from IP address
I'm looking for a command line tool which gets an IP address and returns the host name, for Windows.
- 2,033
230
votes
11
answers
713k
views
"Add correct host key in known_hosts" / multiple ssh host keys per hostname?
Trying to ssh into a computer I control, I'm getting the familiar message:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@...
- 2,483
396
votes
7
answers
974k
views
Why is my crontab not working, and how can I troubleshoot it?
This is a Canonical Question about using cron & crontab.
You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is ...
- 4,371
147
votes
35
answers
572k
views
SSH Suddenly returning Invalid format
So a while ago I set up a server on AWS, and used their generated SSH key. I saved the key to Lastpass, and have successfully retrieved it from there before, and got it working. However, after trying ...
- 1,573
434
votes
15
answers
805k
views
Displaying a remote SSL certificate details using CLI tools
In Chrome, clicking on the green HTTPS lock icon opens a window with the certificate details:
When I tried the same with cURL, I got only some of the information:
$ curl -vvI https://gnupg.org
* ...
- 13.6k
133
votes
14
answers
1.2m
views
How do I force sync the time on Windows Workstation or Server?
What is the command to sync a Windows workstation or server to its configured time source?
- 84.4k
186
votes
6
answers
1.3m
views
314
votes
5
answers
727k
views
Nginx reverse proxy + URL rewrite
Nginx is running on port 80, and I'm using it to reverse proxy URLs with path /foo to port 3200 this way:
location /foo {
proxy_pass http://localhost:3200;
...
- 3,305
160
votes
3
answers
993k
views
What causes the 'Connection Refused' message?
This is a Canonical Question about Connection Refused
We see a lot of questions to the effect
When I try to connect to a system I get a message
Connection refused
Why is this ?
- 116k
84
votes
15
answers
724k
views
Get list of AD groups a user is a member of
Suppose I have the user id of a user in Active Directory. I'd like to get a list of all AD groups in which that user is currently a member of. How can I do this from the Windows command line?
I've ...
- 2,024
554
votes
11
answers
602k
views
In Nginx, how can I rewrite all http requests to https while maintaining sub-domain?
I want to rewrite all http requests on my web server to be https requests, I started with the following:
server {
listen 80;
location / {
rewrite ^(.*) https://mysite.com$1 ...
- 8,502
259
votes
12
answers
585k
views
Docker Container time & timezone (will not reflect changes)
Where do Docker containers get their time information? I've created some containers from the basic ubuntu:trusty image, and when I run it and request 'date', I get UTC time.
For awhile I got around ...
- 2,733
60
votes
8
answers
668k
views
What does "TTL expired in transit" mean on a ping attempt?
We get the message “TTL expired in transit” when we try to ping to a server in a different network segment. When we run tracert, 4 ip addresses repeat themselves indefinitely:
14 60 ms 59 ms ...
- 705
310
votes
14
answers
1.0m
views
What's the command-line utility in Windows to do a reverse DNS look-up?
Is there a built-in command line tool that will do reverse DNS look-ups in Windows? I.e., something like <toolname> w.x.y.z => mycomputername
I've tried:
nslookup: seems to be forward look-...
- 3,235
304
votes
17
answers
739k
views
How to Unban an IP properly with Fail2Ban
I'm using Fail2Ban on a server and I'm wondering how to unban an IP properly.
I know I can work with IPTables directly: iptables -D fail2ban-ssh <number>
But is there not a way to do it with ...
- 3,303
212
votes
6
answers
741k
views
VirtualBox: How to set up networking so both host and guest can access internet and talk to each other
I was wondering if someone could give me a simple guide on how to set up virtual networking in VirtualBox (4.0.2) so that the following scenarios work:
Both Host and Guest can access the Internet
...
- 7,257
151
votes
5
answers
242k
views
What is the difference between authentication and authorization?
Basic question from a novice:
What is the difference between authentication and authorization?
Kyy
259
votes
8
answers
1.0m
views
How do I add Access-Control-Allow-Origin in NGINX?
How do I set the Access-Control-Allow-Origin header so I can use web-fonts from my subdomain on my main domain?
Notes:
You'll find examples of this and other headers for most HTTP servers in the ...
- 3,549
0
votes
0
answers
77k
views
VM down : Failed to read /vm/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/domains: has this domain already been cleaned up?
I'm having a problem with my xcp-ng server, and I'm using the xcp center 20.04.01 on Linux xcp-ng 4.19.0+1. I didn't done anything like update before the issue occurred, everything was working fine ...
- 563
212
votes
13
answers
581k
views
hosts file ignored, how to troubleshoot?
The hosts file on Windows computers is used to bind certain name strings to specific IP addresses to override other name resolution methods.
Often, one decides to change the hosts file, and discovers ...
- 5,345
288
votes
15
answers
544k
views
Finding out what user Apache is running as?
I want to secure a file upload directory on my server as described beautifully here, but I have one problem before I can follow these instructions. I don't know what user Apache is running as.
I've ...
Anna
221
votes
9
answers
1.0m
views
How to check sshd log?
I have Ubuntu 9.10 installed with sshd and I can successfully connect to it using login and password. I have configured an RSA key login and now have "Server refused our key" as expected. Ok, now I ...
- 3,815
206
votes
6
answers
824k
views
How do I convert a .cer certificate to .pem?
I have a .cer certificate and I would like to convert it to the .pem format.
If I remember correctly, I used to be able to convert them by exporting the .cer in Base64, then renaming the file to .pem ...
- 2,205
128
votes
4
answers
1.0m
views
How to check if a port is blocked on a Windows machine?
On the Windows platform, what native options to I have to check if a port (3306, for example) on my local machine (as in localhost), is being blocked?
- 1,393
599
votes
4
answers
347k
views
What exactly do the colors in htop status bars mean?
By default, htop shows colored status bars for processors, memory, and swap. From left to right, the bars are colored green, blue, yellow, and red depending on some thresholds.
What does it mean when ...
- 6,441
146
votes
3
answers
189k
views
How can I upgrade to Java 1.8 on an Amazon Linux Server?
I tried sudo yum update but it just keeps java "1.7.0_75". I need 1.8 for it to work with another application but can't figure out how to upgrade it.
Do I need to manually install it somehow? There's ...
- 1,463
373
votes
19
answers
606k
views
How do I get the current Unix time in milliseconds in Bash?
How do I get the current Unix time in milliseconds (i.e number of milliseconds since Unix epoch January 1 1970)?
- 4,012
170
votes
4
answers
247k
views
Getting "Cannot ioctl TUNSETIFF tun: Operation not permitted" when trying to connect to OpenVPN
I'm trying to setup an OpenVPN Access Server in AWS using the market place AMI, but I;m struggling to connect to it.
The access server is up and running. I've also added a user with Auto-Login and ...
- 5,965
25
votes
9
answers
317k
views
Span on multiple monitors when logged into a Citrix session via Citrix Receiver (or Citrix server)
I am using the Citrix Receiver in Windows 8, and on Windows XP on another PC. I often log into work from home and am unable to span the session to dual monitors like one can easily do when using "...
- 2,024
228
votes
17
answers
723k
views
Permission denied (publickey). SSH from local Ubuntu to Amazon EC2 server
I have an instance of an application running in the cloud on an Amazon EC2 instance, and I need to connect to it from my local Ubuntu. It works fine on one local ubuntu and also laptop. I got this ...
- 2,421
344
votes
27
answers
563k
views
Can I automatically add a new host to known_hosts?
Here's my situation: I'm setting up a test harness that will, from a central client, launch a number of virtual machine instances and then execute commands on them via ssh. The virtual machines will ...
- 9,247
247
votes
17
answers
483k
views
df in linux not showing correct free space after file removal
I have file servers which are used to store files. Files might reside there for a week, or for a year. Unfortunately, when I remove files from the server, df command doesn't reflect the freed up space....
user11350