I'm trying to write a PowerShell script to test user permissions through SSH, the idea is to connect to a distant machine through ssh, then do su to another user and test if we have the permission to do so. I managed to connect to ssh, and send a su command, but the problem is that when I su, I no longer in control with session, so I get stuck into the su user, my question is there a way to solve this issue ?
Regards
Well, you could use the su command with the -c option, which will run a single command and then return (pick a simple command, like hostname). Thereafter you could check the $? variable. If 0, it worked. If non-zero, it failed.
However, if su prompts for a password, then your script is going to get stuck.
sudo, on the other hand, has both a "command" parameter and a "non interactive" parameter. Would sudo work for you?
# -n = Non Interactive
# -u = Username
# -s = Command to run
sudo -n -u root -s hostname
if [ $? == 0 ]; then echo "It worked"; else echo "No good"; fi
I am making a script to securely transfer data between my two machines through scp.
But in the script, it shows an error due to no password. So how can I make my shell script to ask me for password after executing scp command?
Here is my csh script.
# ssh shahk#sj-shahk
# ls -al
echo "Source Location of Remote Server - $1"
echo "Destination Location of Local Server - $2"
echo "File/Folder to be Transferred from Remote Server - $3"
echo "File Transfer Starts"
scp -rv $1/$3 <username>#<hostname>:$2
echo "File Transfer Completed"
# exit
Now I am using the above script with ssh in following way.
ssh <username>#<hostname> "<script name> <args>"
When I use in the above manner, it does not prompt for password while executing scp command.
You can use sshpass
https://www.cyberciti.biz/faq/noninteractive-shell-script-ssh-password-provider/
I have used it once to directly scp or ssh without prompting password.
For example :
sshpass -p 'password' scp file.tar.gz root#xxx.xxx.xxx.194:/backup
As mentioned by the other answer, sshpass will do the job perfectly. In the case where you can not install new packages on your local computer, you can also use expect (installed by default on most distros) to automate your interactive session.
The basic syntax of expect is to wait for the program to display a specific string (expect mystring), which triggers a specific behaviour (send command)
The following script shows the basic structure to implement what you need :
#!/usr/bin/expect -f
# syntax to specify which command to monitor
spawn scp myfile user#remote.host:/dest_folder
# this syntax means we expect the spawned program to display "password: "
# expect can understand regex and glob as well. read the man page for more details
expect "password: "
# the \r is needed to submit the command
send "PASSWORD\r"
# expect "$ " means we wait for anything to be written.
# change if you want to handle incorrect passwords
expect "$ "
send "other_command_to_execute_on_remote\r"
expect "$ "
send "exit\r"
As a side note, you can also set up passwordless authorizations through ssh keys.
#1) create a new ssh key on your local computer
> ssh-keygen -t rsa
#2) copy your public key to your remote server
# you will need to login, but only once. Once the key is on the remote server, you'll be able to connect without password.
> ssh-copy-id -i ~/.ssh/id_rsa.pub user#ip_machine
# OR
> cat ~/.ssh/id_rsa.pub | ssh user#ip_machine "cat - >> ~/.ssh/authorized_keys"
This tutorial explains how to use the keychain tool to manage several ssh keys and users.
ssh <username>#<hostname> "<script name> <args>"
scp will only read a password from a TTY, and it doesn't have a TTY in this case. When you run ssh and specify a command to be executed on the remote system (as you're doing here), ssh by default doesn't allocate a PTY (pseudo-tty) on the remote system. Your script and all of the commands launched from it--including scp--end up running without a TTY.
You can use the ssh -t option to make it allocate a tty on the remote system:
ssh -t <username>#<hostname> "<script name> <args>"
If you get a message like "Pseudo-terminal will not be allocated because stdin is not a terminal", then add another -t:
ssh -tt <username>#<hostname> "<script name> <args>"
I have a bash script that creates backups incrementally(daily) and full(on Mondays). Every 7 days the script combines the week of backups(full and Incremental) and sends them off to an FTP server, the problem i am having is i want to delete the files from my backup directory after the FTP upload is finished, but i cant do that until i know the file was successfully uploaded. I need to figure out how to capture the '226 transfer complete' so i can use that in an 'IF' statement to delete the backup files. Any help is greatly appreciated. also he is my FTP portion of the script
if [ -a "$WKBKDIR/weekending-$YEAR-$MONTH-$DAY.tar.gz" ]; then
HOST=192.168.40.30 #This is the FTP servers host or IP address.
USER=username #This is the FTP user that has access to the server.
PASS=password #This is the password for the FTP user.
ftp -inv $HOST << EOF
user $USER $PASS
cd /baks
lcd $WKBKDIR
put weekending-$YEAR-$MONTH-$DAY.tar.gz
bye
EOF
fi
I could use whatever mean i needed i suppose, FTP was something already setup for another backup function for something else, thanks
2nd EDIT Ahmed the rsync works great in test from command line, its a lot faster than FTP, the server is on the local network so SSH not that big of a deal but nice to have for added security, i will finish implementing in my script tomorrow, thanks again
FTP OPTION
The simple solution would be to do something like this:
ftp -inv $HOST >ftp-results-$YEAR-$MONTH-$DAY.out 2>&1 <<-EOF
user $USER $PASS
cd /baks
bin
lcd $WKBKDIR
put weekending-$YEAR-$MONTH-$DAY.tar.gz
bye
EOF
Also there is an issue with your here-document syntax; there is no space between << and the delimiter word (in your case EOF) and I added a - because you are putting white-spaces before the ACTUAL delimeter (it's tabbed in for the if / fi block) so the [-] is required
Now when you do this; you can parse the output file to look for the successful put of the file. For example:
if grep -q '226 transfer complete' ftp-results-$YEAR-$MONTH-$DAY.out; then
echo "It seems that FTP transfer completed fine, we can schedule a delete"
echo "rm -f $PWD/weekending-$YEAR-$MONTH-$DAY.tar.gz" >> scheduled_cleanup.sh
fi
and just run scheduled_cleanup.sh using cron at a given time; this way you will have some margin before the files are cleaned up
If your remote FTP server has good SITE or PROXY options you may be able to get the remote FTP to run a checksum on the uploaded file after successful upload and return the result.
SCP / RSYNC OPTION
Using FTP is clunky and dangerous, you should really try and see if you can have scp or ssh access to the remote system.
If you can then generate an ssh key if you don't have one using ssh-keygen:
ssh-keygen -N "" -t rsa -f ftp-rsa
put the ftp-rsa.pub file into the $HOST/home/$USER/.ssh/authorized_keys and you have a much nicer method for uploading files:
if scp -B -C weekending-$YEAR-$MONTH-$DAY.tar.gz $USER#$HOST:/baks/ ; then
echo Upload successful 1>&2
else
echo Upload failed 1>&2
fi
Or better yet using rsync:
if rsync --progress -a weekending-$YEAR-$MONTH-$DAY.tar.gz $HOST:/baks/ ; then
echo Upload successful 1>&2
else
echo Upload failed 1>&2
fi
et voilà you are done since rsync works over ssh you are happy and secure
Try the next
#!/bin/bash
runifok() { echo "will run this when the transfer is OK"; }
if [ -a "$WKBKDIR/weekending-$YEAR-$MONTH-$DAY.tar.gz" ]; then
HOST=192.168.40.30 #This is the FTP servers host or IP address.
USER=username #This is the FTP user that has access to the server.
PASS=password #This is the password for the FTP user.
ftp -inv <<EOF | grep -q '226 transfer complete' && runifok
user $USER $PASS
cd /baks
lcd $WKBKDIR
put weekending-$YEAR-$MONTH-$DAY.tar.gz
bye
EOF
fi
test it and when will run ok - replace the echo in the runifok function for your commands what want execute after the upload is succesful.
I wonder why ssh agent forwarding does not work in cron jobs. I have a simple script such as:
ssh -A remote_host "ls ~"
I can run this script without any password typing, but after putting it inside a cron job, it always failed with:
Permission denied, please try again.
Received disconnect from ip_of_remote_host: 2: Too many authentication failures for myuser
Can anyone please tell me how to fix this issue?
Thanks a lot!
you need store SSH_AGENT_PID or SSH_AUTH_SOCK in a env file when your start ssh-agent, and source it in your ssh script,
Here is a script I used, grabbed from web long time ago.
SSH_ENV=$HOME/.ssh/environment
function start_agent {
echo "Initialising new SSH agent..."
/usr/bin/ssh-agent | sed 's/^echo/#echo/' > ${SSH_ENV}
echo succeeded
chmod 600 ${SSH_ENV}
. ${SSH_ENV} > /dev/null
ssh-add id_rsa
}
if [ -f "${SSH_ENV}" ]; then
. ${SSH_ENV} > /dev/null
ps -ef | grep ${SSH_AGENT_PID} | grep ssh-agent$ > /dev/null || {
start_agent;
}
else
start_agent;
fi
run it manually if key is passphase protected, and it will store in the $HOME/.ssh/environment something like
SSH_AUTH_SOCK=/tmp/ssh-KldGwK6643/agent.6643; export SSH_AUTH_SOCK;
SSH_AGENT_PID=6644; export SSH_AGENT_PID;
in your crontab
. $HOME/.ssh/environment && ssh -A blabla
If your server rebooted, you need run the start_agent scrit manually again
You must set environment variable SSH_AUTH_SOCK on ssh client side in order to enable ssh-agent feature (where crontab doesn't set it for you).
*/x * * * * SSH_AUTH_SOCK=agent-sock-file ssh remote "command"
make sure the agent-sock-file exists when the crontab runs
I am trying to write a shell script that creates some directories on a remote server and then uses scp to copy files from my local machine onto the remote. Here's what I have so far:
ssh -t user#server<<EOT
DEP_ROOT='/home/matthewr/releases'
datestamp=$(date +%Y%m%d%H%M%S)
REL_DIR=$DEP_ROOT"/"$datestamp
if [ ! -d "$DEP_ROOT" ]; then
echo "creating the root directory"
mkdir $DEP_ROOT
fi
mkdir $REL_DIR
exit
EOT
scp ./dir1 user#server:$REL_DIR
scp ./dir2 user#server:$REL_DIR
Whenever I run it I get this message:
Pseudo-terminal will not be allocated because stdin is not a terminal.
And the script just hangs forever.
My public key is trusted on the server and I can run all the commands outside of the script just fine. Any ideas?
Try ssh -t -t(or ssh -tt for short) to force pseudo-tty allocation even if stdin isn't a terminal.
See also: Terminating SSH session executed by bash script
From ssh manpage:
-T Disable pseudo-tty allocation.
-t Force pseudo-tty allocation. This can be used to execute arbitrary
screen-based programs on a remote machine, which can be very useful,
e.g. when implementing menu services. Multiple -t options force tty
allocation, even if ssh has no local tty.
Also with option -T from manual
Disable pseudo-tty allocation
Per zanco's answer, you're not providing a remote command to ssh, given how the shell parses the command line. To solve this problem, change the syntax of your ssh command invocation so that the remote command is comprised of a syntactically correct, multi-line string.
There are a variety of syntaxes that can be used. For example, since commands can be piped into bash and sh, and probably other shells too, the simplest solution is to just combine ssh shell invocation with heredocs:
ssh user#server /bin/bash <<'EOT'
echo "These commands will be run on: $( uname -a )"
echo "They are executed by: $( whoami )"
EOT
Note that executing the above without /bin/bash will result in the warning Pseudo-terminal will not be allocated because stdin is not a terminal. Also note that EOT is surrounded by single-quotes, so that bash recognizes the heredoc as a nowdoc, turning off local variable interpolation so that the command text will be passed as-is to ssh.
If you are a fan of pipes, you can rewrite the above as follows:
cat <<'EOT' | ssh user#server /bin/bash
echo "These commands will be run on: $( uname -a )"
echo "They are executed by: $( whoami )"
EOT
The same caveat about /bin/bash applies to the above.
Another valid approach is to pass the multi-line remote command as a single string, using multiple layers of bash variable interpolation as follows:
ssh user#server "$( cat <<'EOT'
echo "These commands will be run on: $( uname -a )"
echo "They are executed by: $( whoami )"
EOT
)"
The solution above fixes this problem in the following manner:
ssh user#server is parsed by bash, and is interpreted to be the ssh command, followed by an argument user#server to be passed to the ssh command
" begins an interpolated string, which when completed, will comprise an argument to be passed to the ssh command, which in this case will be interpreted by ssh to be the remote command to execute as user#server
$( begins a command to be executed, with the output being captured by the surrounding interpolated string
cat is a command to output the contents of whatever file follows. The output of cat will be passed back into the capturing interpolated string
<< begins a bash heredoc
'EOT' specifies that the name of the heredoc is EOT. The single quotes ' surrounding EOT specifies that the heredoc should be parsed as a nowdoc, which is a special form of heredoc in which the contents do not get interpolated by bash, but rather passed on in literal format
Any content that is encountered between <<'EOT' and <newline>EOT<newline> will be appended to the nowdoc output
EOT terminates the nowdoc, resulting in a nowdoc temporary file being created and passed back to the calling cat command. cat outputs the nowdoc and passes the output back to the capturing interpolated string
) concludes the command to be executed
" concludes the capturing interpolated string. The contents of the interpolated string will be passed back to ssh as a single command line argument, which ssh will interpret as the remote command to execute as user#server
If you need to avoid using external tools like cat, and don't mind having two statements instead of one, use the read built-in with a heredoc to generate the SSH command:
IFS='' read -r -d '' SSH_COMMAND <<'EOT'
echo "These commands will be run on: $( uname -a )"
echo "They are executed by: $( whoami )"
EOT
ssh user#server "${SSH_COMMAND}"
I'm adding this answer because it solved a related problem that I was having with the same error message.
Problem: I had installed cygwin under Windows and was getting this error: Pseudo-terminal will not be allocated because stdin is not a terminal
Resolution: It turns out that I had not installed the openssh client program and utilities. Because of that cygwin was using the Windows implementation of ssh, not the cygwin version. The solution was to install the openssh cygwin package.
All relevant information is in the existing answers, but let me attempt a pragmatic summary:
tl;dr:
DO pass the commands to run using a command-line argument:
ssh jdoe#server '...'
'...' strings can span multiple lines, so you can keep your code readable even without the use of a here-document:
ssh jdoe#server ' ... '
Do NOT pass the commands via stdin, as is the case when you use a here-document:
ssh jdoe#server <<'EOF' # Do NOT do this ... EOF
Passing the commands as an argument works as-is, and:
the problem with the pseudo-terminal will not even arise.
you won't need an exit statement at the end of your commands, because the session will automatically exit after the commands have been processed.
In short: passing commands via stdin is a mechanism that is at odds with ssh's design and causes problems that must then be worked around.
Read on, if you want to know more.
Optional background information:
ssh's mechanism for accepting commands to execute on the target server is a command-line argument: the final operand (non-option argument) accepts a string containing one or more shell commands.
By default, these commands run unattended, in a non-interactive shell, without the use of a (pseudo) terminal (option -T is implied), and the session automatically ends when the last command finishes processing.
In the event that your commands require user interaction, such as responding to an interactive prompt, you can explicitly request the creation of a pty (pseudo-tty), a pseudo terminal, that enables interacting with the remote session, using the -t option; e.g.:
ssh -t jdoe#server 'read -p "Enter something: "; echo "Entered: [$REPLY]"'
Note that the interactive read prompt only works correctly with a pty, so the -t option is needed.
Using a pty has a notable side effect: stdout and stderr are combined and both reported via stdout; in other words: you lose the distinction between regular and error output; e.g.:
ssh jdoe#server 'echo out; echo err >&2' # OK - stdout and stderr separate
ssh -t jdoe#server 'echo out; echo err >&2' # !! stdout + stderr -> stdout
In the absence of this argument, ssh creates an interactive shell - including when you send commands via stdin, which is where the trouble begins:
For an interactive shell, ssh normally allocates a pty (pseudo-terminal) by default, except if its stdin is not connected to a (real) terminal.
Sending commands via stdin means that ssh's stdin is no longer connected to a terminal, so no pty is created, and ssh warns you accordingly:
Pseudo-terminal will not be allocated because stdin is not a terminal.
Even the -t option, whose express purpose is to request creation of a pty, is not enough in this case: you'll get the same warning.
Somewhat curiously, you must then double the -t option to force creation of a pty: ssh -t -t ... or ssh -tt ... shows that you really, really mean it.
Perhaps the rationale for requiring this very deliberate step is that things may not work as expected. For instance, on macOS 10.12, the apparent equivalent of the above command, providing the commands via stdin and using -tt, does not work properly; the session gets stuck after responding to the read prompt:
ssh -tt jdoe#server <<<'read -p "Enter something: "; echo "Entered: [$REPLY]"'
In the unlikely event that the commands you want to pass as an argument make the command line too long for your system (if its length approaches getconf ARG_MAX - see this article), consider copying the code to the remote system in the form of a script first (using, e.g., scp), and then send a command to execute that script.
In a pinch, use -T, and provide the commands via stdin, with a trailing exit command, but note that if you also need interactive features, using -tt in lieu of -T may not work.
The warning message Pseudo-terminal will not be allocated because stdin is not a terminal. is due to the fact that no command is specified for ssh while stdin is redirected from a here document.
Due to the lack of a specified command as an argument ssh first expects an interactive login session (which would require the allocation of a pty on the remote host) but then has to realize that its local stdin is no tty/pty. Redirecting ssh's stdin from a here document normally requires a command (such as /bin/sh) to be specified as an argument to ssh - and in such a case no pty will be allocated on the remote host by default.
Since there are no commands to be executed via ssh that require the presence of a tty/pty (such as vim or top) the -t switch to ssh is superfluous.
Just use ssh -T user#server <<EOT ... or ssh user#server /bin/bash <<EOT ... and the warning will go away.
If <<EOF is not escaped or single-quoted (i. e. <<\EOT or <<'EOT') variables inside the here document will be expanded by the local shell before it is executing ssh .... The effect is that the variables inside the here document will remain empty because they are defined only in the remote shell.
So, if $REL_DIR should be both accessible by the local shell and defined in the remote shell, $REL_DIR has to be defined outside the here document before the ssh command (version 1 below); or, if <<\EOT or <<'EOT' is used, the output of the ssh command can be assigned to REL_DIR if the only output of the ssh command to stdout is genererated by echo "$REL_DIR" inside the escaped/single-quoted here document (version 2 below).
A third option would be to store the here document in a variable and then pass this variable as a command argument to ssh -t user#server "$heredoc" (version 3 below).
And, last but not least, it would be no bad idea to check if the directories on the remote host were created successfully (see: check if file exists on remote host with ssh).
# version 1
unset DEP_ROOT REL_DIR
DEP_ROOT='/tmp'
datestamp=$(date +%Y%m%d%H%M%S)
REL_DIR="${DEP_ROOT}/${datestamp}"
ssh localhost /bin/bash <<EOF
if [ ! -d "$DEP_ROOT" ] && [ ! -e "$DEP_ROOT" ]; then
echo "creating the root directory" 1>&2
mkdir "$DEP_ROOT"
fi
mkdir "$REL_DIR"
#echo "$REL_DIR"
exit
EOF
scp -r ./dir1 user#server:"$REL_DIR"
scp -r ./dir2 user#server:"$REL_DIR"
# version 2
REL_DIR="$(
ssh localhost /bin/bash <<\EOF
DEP_ROOT='/tmp'
datestamp=$(date +%Y%m%d%H%M%S)
REL_DIR="${DEP_ROOT}/${datestamp}"
if [ ! -d "$DEP_ROOT" ] && [ ! -e "$DEP_ROOT" ]; then
echo "creating the root directory" 1>&2
mkdir "$DEP_ROOT"
fi
mkdir "$REL_DIR"
echo "$REL_DIR"
exit
EOF
)"
scp -r ./dir1 user#server:"$REL_DIR"
scp -r ./dir2 user#server:"$REL_DIR"
# version 3
heredoc="$(cat <<'EOF'
# -onlcr: prevent the terminal from converting bare line feeds to carriage return/line feed pairs
stty -echo -onlcr
DEP_ROOT='/tmp'
datestamp="$(date +%Y%m%d%H%M%S)"
REL_DIR="${DEP_ROOT}/${datestamp}"
if [ ! -d "$DEP_ROOT" ] && [ ! -e "$DEP_ROOT" ]; then
echo "creating the root directory" 1>&2
mkdir "$DEP_ROOT"
fi
mkdir "$REL_DIR"
echo "$REL_DIR"
stty echo onlcr
exit
EOF
)"
REL_DIR="$(ssh -t localhost "$heredoc")"
scp -r ./dir1 user#server:"$REL_DIR"
scp -r ./dir2 user#server:"$REL_DIR"
I don't know where the hang comes from, but redirecting (or piping) commands into an interactive ssh is in general a recipe for problems. It is more robust to use the command-to-run-as-a-last-argument style and pass the script on the ssh command line:
ssh user#server 'DEP_ROOT="/home/matthewr/releases"
datestamp=$(date +%Y%m%d%H%M%S)
REL_DIR=$DEP_ROOT"/"$datestamp
if [ ! -d "$DEP_ROOT" ]; then
echo "creating the root directory"
mkdir $DEP_ROOT
fi
mkdir $REL_DIR'
(All in one giant '-delimited multiline command-line argument).
The pseudo-terminal message is because of your -t which asks ssh to try to make the environment it runs on the remote machine look like an actual terminal to the programs that run there. Your ssh client is refusing to do that because its own standard input is not a terminal, so it has no way to pass the special terminal APIs onwards from the remote machine to your actual terminal at the local end.
What were you trying to achieve with -t anyway?
After reading a lot of these answers I thought I would share my resulting solution. All I added is /bin/bash before the heredoc and it doesn't give the error anymore.
Use this:
ssh user#machine /bin/bash <<'ENDSSH'
hostname
ENDSSH
Instead of this (gives error):
ssh user#machine <<'ENDSSH'
hostname
ENDSSH
Or use this:
ssh user#machine /bin/bash < run-command.sh
Instead of this (gives error):
ssh user#machine < run-command.sh
EXTRA:
If you still want a remote interactive prompt e.g. if the script you're running remotely prompts you for a password or other information, because the previous solutions won't allow you to type into the prompts.
ssh -t user#machine "$(<run-command.sh)"
And if you also want to log the entire session in a file logfile.log:
ssh -t user#machine "$(<run-command.sh)" | tee -a logfile.log
I was having the same error under Windows using emacs 24.5.1 to connect to some company servers through /ssh:user#host. What solved my problem was setting the "tramp-default-method" variable to "plink" and whenever I connect to a server I ommit the ssh protocol. You need to have PuTTY's plink.exe installed for this to work.
Solution
M-x customize-variable (and then hit Enter)
tramp-default-method (and then hit Enter again)
On the text field put plink and then Apply and Save the buffer
Whenever I try to access a remote server I now use C-x-f /user#host: and then input the password. The connection is now correctly made under Emacs on Windows to my remote server.