Some (trivial?) commands to work on a remote machine using the SSH, FTP and HTTP protocols.
Generate SSH keys for using a SSH connection without having to enter the password every time you log in.
Generate the key (local machine) [Skip this step if you have already the keys in your machine!]:
cd ~/.ssh # create dir if it doesn't exist
ssh-keygen -t rsa -C "[email protected]"
chmod 700 id_rsa
ssh-keygen will create two files with the private and public keys: id_rsa and id_rsa.pub.
Log on the remote host (remote machine):
ssh [email protected]
cd ~/.ssh # create dir if it doesn't exist
Copy your public key (local machine):
cat ~/.ssh/id_rsa.pub
Paste the public key to the remote host (remote machine):
vim ~/.ssh/authorized_keys # create dir and file if they don't exist
chmod 644 ~/.ssh/authorized_keys # change file permissions
Log on the remote machine without entering the password. If necessary, give the path to your private key (usually not needed!):
ssh -i ~/.ssh/id_rsa [email protected]
Read more about SSH keys.
Restart a local computer immediately:
sudo shutdown -r now
Restart a remote computer at a specific time:
ssh -l root computer shutdown -r hhmm
Shut down a remote computer in 30 minutes:
ssh -l root computer shutdown -h +30
A job (or process) is defined as an "instance" of an executing program.
List the jobs in your job table:
jobs
Kill job number [2] on the list:
kill %2
Display information about your processes running:
ps
Some ps options::
-f Displays full information.
-e Displays all processes running.
-u *username* Displays user processes including those from other sessions.
Kill process by PID number:
kill 3682
Kill process by name:
pkill name
Note: if you try to logout and get the message
There are stopped jobs
list the jobs (using jobs) and kill the stopped jobs or bring them to the foreground (see bellow), or simply type: logout logout (yes, twice).
Run a job in the background with &:
nohup commands &
nohup enables the command to keep running after the user has logged out. The output that would normally go to the terminal goes to a file called nohup.out if it has not already been redirected (e.g., > file.out).
Bring a background (or stopped) job to the foreground:
fg %jobnumber
Place a foreground job in the background (to free the terminal):
^Z # type Control-z to suspend de job
bg
Monitor (in "real time") the main processes running and information about system/hardware usage (e.g., CPU, memory, network, etc.):
top
Read more about job control.
scp is an application to copy files to, from, or between different hosts. It uses SSH for data transfer and provides the same authentication and same level of security as SSH.
rsync is an application to analyse files and only copy the changes made to files rather than all files. See option bellow for SSH transfer protocol. The rest, similar syntax as scp.
Copy file from remote host to local host:
scp [email protected]:/remote/file.ext /local/directory
Copy file from local host to remote host:
scp file.ext [email protected]:/remote/directory
Copy file from remote host1 to remote host2:
scp [email protected]:/remote/file.ext [email protected]:/remote/directory
Copy multiple files from local host to remote host:
scp file1.ext file2.ext files3.ext [email protected]:/remote/directory
Note: for more than a few files, as scp spawns a new process for each file, use rsync instead.
Some scp options::
-r Recursively go through directories.
-C Compress the data before it goes over the network.
Note: -r does not know about symbolic links and will blindly follow them.
Some rsync options::
-a Archive mode, preserves file permissions and does not follow symlinks.
-z Enable compression. Compress each file as it gets sent through the pipe.
-e ssh Uses SSH as the transport.
-v Verbose, lists files being copied.
Obs: use of trailing slashes can be confusing.
Interactive
ftp is an application (client) to transfer files between computers connected via the File Transfer Protocol (FTP).
Connect to the remote host:
ftp remote.host.edu
For a public FTP use
user: [email protected]
password: anonymous
Change dir and see content:
cd dirname
ls
Copy file from remote host to local host (initial local dir):
get remotefile.ext
Copy file from local host (initial local dir) to remote host:
put localfile.ext
Copy multiple files (to/from initial local dir):
mget *.ext
mput *.ext
For not answering (Y/N) type: prompt off.
Close the connection:
quit
Non-interactive
For non-interactive download you can use wget or curl.
List directory:
wget ftp://ftp.host.name.edu/pub/directory/ # this will generate an index.html file
open index.html # whole directory structure listing
or
curl ftp://ftp.host.name.edu/pub/directory/
Put the trailing slashes on directories.
Get files:
wget ftp://ftp.host.name.edu/pub/directory/*.ext
or
curl ftp://ftp.host.name.edu/pub/directory/file.ext -O # no globbing
Some wget options:
--ftp-user=user Specifies the username.
--ftp-password=password Specifies the password.
-r Recursive download.
-m Keep a mirror of a directory (-r -N -l).
-c Resume getting a partially-downloaded file.
-A Comma-separated list of accepted extensions.
-R Comma-separated list of rejected extensions.
Some curl options:
--user username:password Specify user and password.
This is non-recursive!
Download a whole website keeping the original structure (mirror):
wget -m http://www.website.com/
Download recursively all .html files from a website directory:
wget -r -A.html http://www.website.com/directory/