If I want to find a file by name, I do the following:
find -name app
If I want to find a file by type, I do the following:
find -name app -type d
However, because app is such a generic name, many results show up. I would like to find a directory named app, which was created today. Is there a flag or command to achieve this?
I want to block traffic to a specific domain e.g. mysite.com. I tried blocking the ip address of the site but it does not work:
ufw deny from 0.0.0.0 to ip_address_of_site
I am still able to acess the website, even after a reboot.
Any idea what I might be doing wrong?
The locate command sounds intuitive. I would expect it to locate files on the filesystem. However, it rarely finds files on the system that are indeed present:
$ locate ipsec.secrets
This gives no results, even when run from filesystem root directory /. The file is indeed present:
$ whereis ipsec.secrets
ipsec: /usr/sbin/ipsec /etc/ipsec.secrets /etc/ipsec.d /etc/ipsec.conf /usr/lib/ipsec /usr/share/man/man8/ipsec.8.gz
Why was locate unable to find this file?
I am following this bash shell scripting guide:
In the section Numeric Comparisons, it cites an example:
anny > num=`wc -l work.txt`
anny > echo $num
201
anny > if [ "$num" -gt "150" ]
More input> then echo ; echo "you've worked hard enough for today."
More input> echo ; fi
What seems to happen above is we store a string of commands in a bash variable and then we invoke echo on the variable. What seems to happen is the string is evaluated and the wc command is executed and returns the line count to the controlling terminal.
Ok, so I launch my terminal in Ubuntu 12.04 and try something similar:
$ touch sample.txt && echo "Hello World" > sample.txt
$ cat sample.txt
Hello World
$ num='wc -l sample.txt'
echo $num
wc -l sample.txt
Wait a second, that didn't evaluate the string and return the line count. That just echoed the string back to the terminal. Why did I get different results?
Using Ubuntu Desktop, I have terminal open and I am using the bash shell. One of the shell expansions of bash is the arithmetic expansion, with the following syntax:
$(( EXPRESSION ))
or
$[ EXPRESSION ]
When i do arithmetic, it does return the correct value but it is always followed by "command not found":
$ $((1+2))
3: command not found
$ $[1+2]
3: command not found
$ $[2+2]
4: command not found
$ $((2*6))
12: command not found
My question is why does it display "command not found" and how can I fix that?
I got ssh key authentication working on my production server quite swiftly. However, I have been struggling to get it to work on my development server.
First, I generated the keys (I use Ubuntu on both home and server):
$ ssh-keygen -t rsa -f ~/.ssh/production-key.id_rsa
.ssh$ ls -l
total 36
-rw-rw-r-- 1 viggy viggy 234 Dec 22 15:21 config
-rw------- 1 viggy viggy 1766 Dec 22 15:03 development-key.id_rsa
-rw-r--r-- 1 viggy viggy 397 Dec 22 15:03 development-key.id_rsa.pub
-rw------- 1 viggy viggy 1766 Dec 22 13:12 production-key.id_rsa
-rw-r--r-- 1 viggy viggy 397 Dec 22 13:12 production-key.id_rsa.pub
-rw------- 1 viggy viggy 1766 Sep 5 20:36 id_rsa
-rw-r--r-- 1 viggy viggy 403 Sep 5 20:36 id_rsa.pub
-rw-r--r-- 1 viggy viggy 4422 Dec 22 11:45 known_hosts
I added development private key to my config file:
vim config
Host production
HostName xx.xxx.xx.xxx
User myuser
IdentityFile ~/.ssh/production-key.id_rsa
Host development
HostName xx.xxx.xx.xxx
User myuser
IdentityFile ~/.ssh/development-key.id_rsa
Then I copied public key to server:
cd ~/.ssh
vim authorized_keys // deleted contents of this file and copied my development-key.id_rsa.pub into it and saved file
cat authorized_keys // looked at contents to confirm it matched my development-key.id_rsa.pub
Then I tried to ssh into development server, but it asked for my password (rather than prompting for passphrase).
So next I began to troubleshoot why it didn't work. I checked the file/directory permissions on server:
$ ls -l | grep home
drwxr-xr-x 6 root root 4096 Aug 7 2012 home
$ ls -l | grep myuser
drwxr-xr-x 16 myuser myuser 4096 Dec 22 17:47 myuser
$ ls -la | grep .ssh
drwx------ 3 myuser myuser 4096 Dec 22 15:32 .ssh
~/.ssh $ ls -l | grep authorized_keys
-rw------- 1 myuser myuser 396 Dec 22 15:32 authorized_keys
Next I looked at the sshd_config file to confirm its configurations. Now I do not have password authentication disabled yet, but I don't have it disabled on my other server either and the ssh keys worked:
$ cd /etc/ssh
$ head -n 1000 sshd_config | grep 'PasswordAuthentication'
#PasswordAuthentication yes
I checked to see if any accounts were not allowed access to ssh (but there was nothing unusual here):
$ head -n 1000 sshd_config | grep 'AllowUsers'
$ head -n 1000 sshd_config | grep 'DenyUsers'
I made sure public key authentication was enabled:
head -n 1000 sshd_config | grep 'PubkeyAuthentication'
PubkeyAuthentication yes
$ head -n 1000 sshd_config | grep 'RSAAuthentication'
RSAAuthentication yes
RhostsRSAAuthentication no
I then restarted the ssh server:
sudo restart ssh
I then checked if my home directory is encrypted but it's not:
ls -A /home
.directory lost+found quota.group someuser
myuser passenger quota.user
I checked perhaps there was some other configuration on the system:
/ $ locate sshd_config
/etc/ssh/sshd_config
/usr/share/doc/openssh-client/examples/sshd_config
/usr/share/man/man5/sshd_config.5.gz
I tried the suggestions here:
ssh no longer allows public key authentication
So finally I tried ssh in debug mode, and this is what I got (I changed the ip address and usernames):
ssh -vv [email protected]
OpenSSH_5.9p1 Debian-5ubuntu1.1, OpenSSL 1.0.1 14 Mar 2012
debug1: Reading configuration data /home/viggy/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to xx.xxx.xx.xxx [xx.xxx.xx.xxx] port 22.
debug1: Connection established.
debug1: identity file /home/viggy/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/viggy/.ssh/id_rsa-cert type -1
debug1: identity file /home/viggy/.ssh/id_dsa type -1
debug1: identity file /home/viggy/.ssh/id_dsa-cert type -1
debug1: identity file /home/viggy/.ssh/id_ecdsa type -1
debug1: identity file /home/viggy/.ssh/id_ecdsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1.1
debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1.1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.9p1 Debian-5ubuntu1.1
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: [email protected],[email protected],ssh-rsa,[email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: RSA 42:f0:18:ae:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
debug1: Host 'xx.xxx.xx.xxx' is known and matches the RSA host key.
debug1: Found key in /home/viggy/.ssh/known_hosts:3
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/viggy/.ssh/id_rsa (0xb8bab790)
debug2: key: viggy@teamviggy (0xb8bb1e18)
debug2: key: viggy@teamviggy (0xb8bb1cb8)
debug2: key: /home/viggy/.ssh/id_dsa ((nil))
debug2: key: /home/viggy/.ssh/id_ecdsa ((nil))
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/viggy/.ssh/id_rsa
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,password
debug1: Offering RSA public key: viggy@teamviggy
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,password
debug1: Offering RSA public key: viggy@teamviggy
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /home/viggy/.ssh/id_dsa
debug1: Trying private key: /home/viggy/.ssh/id_ecdsa
debug2: we did not send a packet, disable method
debug1: Next authentication method: password
[email protected]'s password:
UPDATE: So I used my public production key on my development server and that worked. So apparently something in my ~/.ssh/config file is incorrect but I am not sure what.
"The sticky bit applies only to directories, and is typically used on publicly-writeable directories. Within a directory upon which the sticky bit is applied, users are prevented from deleting or renaming any files that they do not personally own."
Does this mean if I run the following:
// only allow other users to read files in /directory
sudo chmod o-w -R /directory
sudo chmod o-x -R /directory
sudo chmod o+r -R /directory
users can still delete or rename any file that does not belong to them?
I tried to delete a user:
# deluser someuser
Removing user `someuser' ...
Warning: group `someuser' has no more members.
userdel: user someuser is currently logged in
/usr/sbin/deluser: `/usr/sbin/userdel someuser' returned error code 8. Exiting.
I ran who
# who
myuser pts/0 2013-12-19 23:00 ...
It only shows me logged in. I really need to delete this user but I don't have their password, I have sudo password however. How can I delete it?
I am logged into Ubuntu server via ssh and I would like to know if another user is logged in via SSH as well. Is there a command that I can run to accomplish this?
My web server was tampered by someone who was using zsh shell. I feel more comfortable using bash shell, as that's the defaults that come with Ubuntu and OS X (the two main operating systems I use). But this questions is focused on Ubuntu server.
I have 4 websites running on this web server, I use byobu, I use tmux, I use ruby/ruby on rails, node.js, Apache, a few daemons. If I switch the current root shell from zsh to bash, could there be any negative side effects that might result from this switch? For example, will processes be killed because their parent process (the shell) has been switched?
On a few of my ubuntu installations, when I run sudo su and become sudo user, I can type history and view a list of commands run as sudo user. However, on my one ubuntu installation, for some reason when I run sudo su and type history, I just get this:
$ sudo su
# history
1 history
But I know for certain that a lot of commands were run as sudo user, but when I ssh out and ssh back into my ubuntu server, they do not display, like how they do on the other servers. Do I have some switch or something disabled on this one server? How can I regain access to view the history of commands run as sudo user?
I am trying to copy from the terminal with xclip and paste it into the unity desktop environment into gedit text editor. I can copy and paste with xclip in terminal:
$ cat line-size.c | xclip
xclip -o > input5.txt
cat input5.txt
#include <stdio.h>
...
However, when I press control + v to paste into gedit, it only pastes the actual last thing I copied within unity desktop, such as something from firefox browser.
How can I paste in gui applications something I copied from terminal?
I'm trying to kill a screen session. I noticed a lot of other related questions, but none of those answers are working for me. I am trying to kill the following session:
screen -ls
There is a screen on:
23520.pts-6.porkypig (09/30/2013 02:49:47 PM) (Detached)
1 Socket in /var/run/screen/S-root.
screen -r 23520.pts-6.porkypig
Now I am in the session. According to the documentation:
http://www.gnu.org/software/screen/manual/screen.html#Quit
I am supposed to press "control a" and then "control \". I do that and nothing happens.
Another solution said to press Ctrl+a and type :quit. However, again it doesn't do anything. In fact, pressing control+a, absolutely nothing happens afterwards except a message "No Other Window"
Does Ubuntu use SELinux by default and if not, how is security context managed? For example, allowing processes to run as root without security context can be a security risk.
The help page about SELinux suggests that SELinux is a program that needs to be manually installed.
So then how does Ubuntu handle security context out of the box?
I have a program running under screen. In fact, when I detach from the session and check netstat, I can see the program is still running (which is what I want):
udp 0 0 127.0.0.1:1720 0.0.0.0:* 3759/ruby
Now I want to reattach to the session running that process. So I start up a new terminal, and type screen -r
$ screen -r
There are several suitable screens on:
5169.pts-2.teamviggy (05/31/2013 09:30:28 PM) (Detached)
4872.pts-2.teamviggy (05/31/2013 09:25:30 PM) (Detached)
4572.pts-2.teamviggy (05/31/2013 09:07:17 PM) (Detached)
4073.pts-2.teamviggy (05/31/2013 08:50:54 PM) (Detached)
3600.pts-2.teamviggy (05/31/2013 08:40:14 PM) (Detached)
Type "screen [-d] -r [pid.]tty.host" to resume one of them.
But how do I know which one is the session running that process I created?
Now one of the documents I came across said:
"When you're using a window, type C-a A to give it a name. This name will be used in the window listing, and will help you remember what you're doing in each window when you start using a lot of windows."
The thing is when I am in a new screen session, I try to press control+a A and nothing happens.
I have a small program I created. Here is a relevant piece of it:
void TcpSocket::ConnectSocket()
{
socket = new QTcpSocket(this);
socket->connectToHost("localhost", 77);
if(socket->waitForConnected(3000)){
qDebug() << "Connected";
socket->write("Hello Server\n\r\n");
socket->waitForBytesWritten(1000);
socket->waitForReadyRead(3000);
qDebug() << "Reading: " << socket->bytesAvailable();
qDebug() << socket->readAll();
socket->close();
}
else {
qDebug() << "Could not connect";
}
}
Basically, I want to open a tcp socket at localhost:77. I want to write some data to it, get a response, and then output the response. However, right now that port is closed, as most ports are in ubuntu by default. So right now it cannot connect to that port to listen on. Well from what I researched, iptables seems to be the only way to open a port for listening. So I run this line on my machine:
sudo iptables -A INPUT -p tcp --dport 77 -j ACCEPT
However, the port 77 is still not open.
sudo netstat -tulpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 1199/dnsmasq
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1004/cupsd
tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN 1157/postgres
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 1121/mysqld
tcp6 0 0 ::1:631 :::* LISTEN 1004/cupsd
udp 0 0 127.0.0.1:53 0.0.0.0:* 1199/dnsmasq
udp 0 0 0.0.0.0:68 0.0.0.0:* 1070/dhclient
udp 0 0 0.0.0.0:39617 0.0.0.0:* 990/avahi-daemon: r
udp 0 0 0.0.0.0:5353 0.0.0.0:* 990/avahi-daemon: r
udp6 0 0 :::57021 :::* 990/avahi-daemon: r
udp6 0 0 :::5353 :::* 990/avahi-daemon: r
netstat doesnt show it to be open. Also I still have the same problem with my program: it cannot connect to 77.
When you install Ubuntu server, the default Ubuntu server will only store the core system, but there is an option to add additional server roles. One of these is a "DNS Server".
From what I read, when you add this choice to your installation, Ubuntu adds the bind9 and bind9-doc packages to your system. These packages provide the Bind 9 DNS server and its documentation. Now in fact a DNS server is simply a technology that takes a host name and automatically finds the IP address for that host on the Internet. Whenever you purchase a domain, for example, on Godaddy, you have the option on their website to point that hostname at your public IP address. It's that simple. So why would anyone need to set up a DNS server on their Ubuntu installation?
My understanding of disc partitioning has always been that you partition a disc to install multiple operating systems so you can boot from multiple operating systems on a single disc. However I'm reading a ubuntu server book and it talks about partitioning the /home directory of a ubuntu installation.
"The /home directory is a popular partitioning candidate among both administrators and desktop users alike because it holds all of the personal files for user accounts on that machine. If you maintain /home as a separate partition, you can install new versions of a distribution or even different distributions altogether without wiping out any user settings."
I don't see how and why anyone would partition the home directory or any other directory for that matter in the file system of a ubuntu installation.
I have a running log, it outputs a lot to the terminal. Unfortunately, when I try to scroll up and view older output, it appears there is a limit. And I am unable to scroll past a certain point. On the Mac, the terminal allows you to scroll up to the start of the session. Is there a way to do this in ubuntu terminal?
I know this is possible duplicate but I looked at other answers and wasn't satisfied with the responses. You should be able to use the chown command if you are the super user OR the owner of the file. Well, in my case I am the owner of the file, and I want to use chown. But I want to change ownership of file to super user, so I type following:
$ chown root testfile
But it gives me error:
chown: changing ownership of `testfile': Operation not permitted
However, I am the owner of the file, and granted myself read, write, and execute permission on the file:
-rwx------ 1 viggy viggy 10 Nov 14 13:01 testfile
So as the owner of the file, why can I not change ownership of the file?