All Questions
325,473
questions
221
votes
10
answers
208k
views
How to install tzdata on a ubuntu docker image?
I have the following line in the Dockerfile.
RUN apt-get install -y tzdata
When I run it, it asks for my input. After I provided my input, it hung there. Does anybody know how to solve this problem?
...
- 2,369
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
220
votes
7
answers
459k
views
Nginx config reload without downtime
I use nginx as a reverse proxy.
Whenever I update the config for it using
sudo "cp -r #{nginx_config_path}* /etc/nginx/sites-enabled/"
sudo "kill -s HUP `cat /var/run/nginx.pid`"
I face a brief ...
- 2,315
218
votes
5
answers
213k
views
Difference in sites-available vs sites-enabled vs conf.d directories (Nginx)?
I have some experience using linux but none using nginx. I have been tasked with researching load-balancing options for an application server.
I have used apt-get to install nginx and all seems ...
- 2,341
218
votes
8
answers
357k
views
Setting the hostname: FQDN or short name?
I've noticed that the "preferred" method of setting the system hostname is fundamentally different between Red Hat/CentOS and Debian/Ubuntu systems.
CentOS documentation and the RHEL ...
- 25.6k
217
votes
16
answers
164k
views
How do diff over ssh?
How do I diff files/folders across machines provided that the only connectivity available is ssh?
- 3,531
216
votes
11
answers
341k
views
How to read backward from the end of file in less or more?
I've found one way so far: less +G filename, but it scrolls up line-by-line only with ↑.
What's a more powerful less usage which provides scrolling by page, backward pattern search, and so on?
- 2,265
215
votes
18
answers
387k
views
How to use rsync over FTP
Any unix:
I have the following cmd line which works fine.
rsync -avr -e ssh /home/dir [email protected]:/home/
But I need to set it up now to rsync to a remote server that only has an FTP server on ...
- 2,353
215
votes
8
answers
351k
views
How to setup passwordless `sudo` on Linux?
How can passwordless sudo access be setup on either RHEL (Fedora, CentOS, etc) or Ubuntu distributions? (If it's the same across distros, that's even better!)
Setting: personal and/or lab/training ...
- 18.7k
214
votes
10
answers
528k
views
How to refresh hosts file without rebooting
On Windows, how do you refresh the hosts file without rebooting?
kakridge
213
votes
1
answer
222k
views
SSH use only my password, Ignore my ssh key, don't prompt me for a passphrase
This is a question regarding the OpenSSH client on Linux, MacOSX and FreeBSD.
Normally, I log into systems using my SSH key.
Occasionally, I want my SSH client to ignore my SSH key and use a ...
- 24k
212
votes
13
answers
580k
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
212
votes
6
answers
740k
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
211
votes
8
answers
218k
views
How do you validate fstab without rebooting?
I modified /etc/fstab.
I verified the new devices and I can mount them with the mount command.
How may I validate the modifications made to /etc/fstab ?
- 3,310
208
votes
15
answers
372k
views
How to reconnect to a disconnected ssh session
Is there a way to connect to an ssh session that was disconnected? We are having problems with our network connection to a remote site that we are working on separately; however, in the mean time we ...
- 4,369
207
votes
9
answers
250k
views
Check if array is empty in Bash
I have an array which gets filled with different error messages as my script runs.
I need a way to check if it is empty of not at the end of the script and take a specific action if it is.
I have ...
- 2,081
207
votes
3
answers
117k
views
Possible to change email address in keypair?
I've created an RSA keypair that I used for SSH, and it includes my email address. (At the end of the public key.)
I've now changed my email address.
Is it possible to change the email address on ...
- 5,301
206
votes
3
answers
181k
views
Difference between KVM and QEMU
I have been reading about KVM and Qemu for sometime. As of now I have a clear understanding of what they do.
KVM supports hardware virtualization to provide near native performance to the Guest ...
- 2,195
206
votes
6
answers
822k
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
206
votes
4
answers
283k
views
Meaning of the buffers/cache line in the output of free
Why does my server show
total used free shared buffers cached
Mem: 12286456 11715372 571084 0 81912 6545228
-/+ buffers/cache: 5088232 7198224
Swap:...
- 2,163
205
votes
5
answers
155k
views
What is a glue record?
This is a Canonical Question about DNS glue records.
What exactly (but briefly) is a DNS glue record? Why are they needed and how do they work?
- 3,127
204
votes
3
answers
179k
views
How do I ask apt-get to skip any interactive post-install configuration steps?
I have a server build script which uses apt-get to install packages. It then puts pre-written configuration files directly in place, so the interactive post-install configuration dialog in packages ...
- 2,635
204
votes
9
answers
569k
views
How to start/stop/restart launchd services from the command line?
How do I restart, say for example my httpd or afpd, running any Mac OS X >= 10.5 (Leopard-), without having to use the GUI and go to System Preferences -> Sharing and unchecking/checking "Web Sharing"?...
- 2,429
204
votes
9
answers
33k
views
Heartbleed: What is it and what are options to mitigate it?
This is a Canonical Question about understanding and remediating the Heartbleed security issue.
What exactly is CVE-2014-0160 AKA "Heartbleed"? What is the cause, what OSs and versions of OpenSSL are ...
- 9,242
203
votes
6
answers
190k
views
Non interactive git clone (ssh fingerprint prompt) [duplicate]
I want to clone a repo in a non-interactive way. When cloning, git asks to confirm host's fingerprint:
The authenticity of host 'bitbucket.org (207.223.240.182)' can't be established.
RSA key ...
- 2,077
202
votes
14
answers
258k
views
How to view all ssl certificates in a bundle?
I have a certificate bundle .crt file.
doing openssl x509 -in bundle.crt -text -noout only shows the root certificate.
how do i see all the other certificates?
- 2,517
202
votes
1
answer
211k
views
What is a challenge password?
I'm setting up SSL on an Ubuntu server. One of fields it asks for as part of setting up the CSR is a "challenge password". What is that? The default is blank. Do I need to enter one?
- 2,513
200
votes
5
answers
629k
views
How to sleep in a batch file?
How to pause execution for a while in a Windows batch file between a command and the next one?
- 71.3k
200
votes
3
answers
203k
views
What does a + mean at the end of the permissions from ls -l?
What is the plus sign at the end of the permissions telling me?
ls -l
total 4
drwxrwxrwx+ 2 benson avahi-autoipd 4096 Jan 27 17:37 docs
Here's the context:
cat /etc/issue
\CentOS release 5.3 (Final)...
- 2,403
198
votes
11
answers
110k
views
ssh-agent forwarding and sudo to another user
If I have a server A into which I can login with my ssh key and I have the ability to "sudo su - otheruser", I lose key forwarding, because the env variables are removed and the socket is only ...
Florian Schulze
196
votes
6
answers
65k
views
How to cd into a directory with this name "-2" (starting with the hyphen)?
I have a directory named:
-2
I want to cd into it but the cd complains:
bash: cd: -2: invalid option
With no success, I've tried:
cd "-2"
cd '-2'
cd \-2
Any solution?
Edit: no file browsers ...
- 1,863
196
votes
22
answers
111k
views
Is it normal to get hundreds of break-in attempts per day?
I just checked my server's /var/log/auth.log and found that I'm getting over 500 failed password/break-in attempt notifications per day! My site is small, and its URL is obscure. Is this normal? ...
- 1,537
196
votes
6
answers
85k
views
LVM dangers and caveats
I have recently started using LVM on some servers for hard drives larger than 1 TB. They're useful, expandable and quite easy to install. However, I could not find any data about the dangers and ...
- 13.6k
195
votes
10
answers
507k
views
Nginx enable site command
We all know how to enable a website using apache on Linux.
I'm pretty sure that we all agree on using the a2ensite command.
Unfortunately, there is no default equivalent command that comes with Nginx, ...
- 3,105
194
votes
13
answers
212k
views
Top level domain/domain suffix for private network?
At our office, we have a local area network with a purely internal DNS setup, on which clients all named as whatever.lan. I also have a VMware environment, and on the virtual-machine-only network, I ...
- 2,171
194
votes
6
answers
213k
views
how to disable SSH login with password for some users?
On Linux (Debian Squeeze) I would like to disable SSH login using password to some users (selected group or all users except root). But I do not want to disable login using certificate for them.
edit:...
- 2,159
194
votes
15
answers
358k
views
How to know from which yum repository a package has been installed?
After I have installed a package by yum (with multiple repositories configured), how can I find from which repository it has been installed?
If I run yum info package-name (or yum list package-name), ...
- 4,679
192
votes
10
answers
663k
views
How do I verify the speed of my NIC?
I just installed a new gigabit network interface card (NIC) in Linux. How do I tell if it is really set to gigabit speeds? I see ethtool has an option to set the speed, but I can't seem to figure ...
- 2,556
191
votes
10
answers
319k
views
What is "-bash: !": event not found"
Try executing the following under a bash shell echo "Reboot your instance!"
On my installation:
root@domU-12-31-39-04-11-83:/usr/local/bin# bash --version
GNU bash, version 4.1.5(1)-release (i686-pc-...
- 2,805
191
votes
5
answers
457k
views
DNS - NSLOOKUP what is the meaning of the non-authoritative answer?
For some domains nslookup gives me a Non-authoritative answer section. What does this mean?
Got answer:
HEADER:
opcode = QUERY, id = 3, rcode = NXDOMAIN
header flags: response, ...
- 4,432
191
votes
5
answers
27k
views
I am under DDoS. What can I do?
This is a Canonical Question about DoS and DDoS mitigation.
I found a massive traffic spike on a website that I host today; I am getting thousands of connections a second and I see I'm using all ...
- 25.3k
190
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.
- 2,023
190
votes
6
answers
499k
views
SSL Certificate Location on UNIX/Linux
Is there any standard or convention for where SSL certificates and associated private keys should go on the UNIX/Linux filesystem?
- 2,205
190
votes
2
answers
48k
views
What are the different widely used RAID levels and when should I consider them?
This is a Canonical Question about RAID levels.
What are:
the RAID levels typically used (including the RAID-Z family)?
deployments are they commonly found in?
benefits and pitfalls of each?
- 101k
190
votes
4
answers
83k
views
Should I quit using Ifconfig?
With the servers that mount Infiniband cards, when I use the ifconfig command, I get this warning:
Ifconfig uses the ioctl access method to get the full address
information, which limits hardware ...
- 2,159
189
votes
12
answers
16k
views
Physically locating the server
I've got a CentOS server somewhere in the building; I can login into it remotely and VNC, etc. Now I've got to physically move it, and for that I need to physically locate the machine among the ...
- 1,723
187
votes
13
answers
44k
views
Why couldn't MAC addresses be used instead of IPv4|6 for networking? [closed]
I am reading up on TCP/IP and other related protocols and technologies. MAC addresses are described as being (reasonably :) unique, and as having a large possibility space (several hundred trillions), ...
- 1,393
187
votes
73
answers
247k
views
What tool do you use to monitor your servers?
For a more comprehensive list of monitoring tools and their features, check out this Wikipedia page.
As the question states, what are the most commonly used tools used for this task and what are ...
186
votes
6
answers
1.3m
views
185
votes
14
answers
306k
views
How to create a UUID in bash?
In Java it is possible to create a random UUID:
UUID uuid = UUID.randomUUID();
How to do this in Bash?
- 4,823