I want to change root password of multiple server's. I used shell with for loop and chpasswd utility to do this. Since the sudo account is password enabled, it is prompting sudo password all the time I exit script.
Below is bash Script is written in bash. But always prompting for password.
#!/bin/bash
pass="PASSWORD"
for i in $(cat serverlist)
do
ssh -t sudouser#$i "sudo chpasswd <<EOF
root:"$pass"
EOF" ;
done
Completely automated bash to change root password.
I also think you should use expect. The script I've written isn't fully tested, since I don't have a server which I'm conformable on to change passwords :-)
#!/bin/bash
read -p "Server username? " USERNAME
read -sp "Server password for ${USERNAME}? " PASSWORD
echo
read -p "Name of file containing server list? " S_FILE
read -p "User to change on servers? " S_USERNAME
read -sp "New password for user ${S_USERNAME}?" S_PASSWORD
echo
while IFS= read -r SERVER; do
[ ! -z "${SERVER}" ] || continue
expect <<-EOF
spawn ssh ${USERNAME}#${SERVER}
expect "*: " { send "${PASSWORD}\r" }
expect "*$ " { send "echo '${S_USERNAME}:${S_PASSWORD}' | sudo chpasswd\r" }
expect "*: " { send "${PASSWORD}\r" }
expect "*$ " { send "exit\r" }
EOF
echo
done < ${S_FILE}
exit $?
Writing a script to do unattended root things is dangerous. All you need is one machine to somehow behave differently than you expect and your automated approach wouldn't work. Worse, you could end up in some bad state, possibly without even realizing that anything went wrong.
This sounds like a great fit for csshx (or something similar). Use it to manually apply whatever changes you want in parallel across multiple hosts. For example, you could connect to 16 hosts at once like this:
csshx host[1-16]
then type commands and watch output for each host.
If this seems infeasible due to the number of machines you have, I would counter that it's much safer than scripting, and - even if "slow" - the overall time spent might very well be less than that of trying to create an automated solution. ;)
how can we write a simple regular function which i can put in my bashprofile
which can be used to secure console to any host i want.
but my secure console has to go through a jump host. that is the issue.
function func_name () {
ssh jumphostname;
sc $hostname # from jump host secure console to another host given as input from terminal
}
this function only making to login in to jump host but not to secureconsole in to another host from there.
-bash-4.1$func_name host.me.com
should give me console to host.me.com via jumphost
is function for this not possible?
do i have to write a script?
Here's how I do it.
Create a functions folder at home
Write my function as a shell script
Reference the file as an alias in my bash_profile
Reset the source
Example
mkdir ~/.functions
echo '#!/bin/bash
echo $1' > ~/.functions/ekho
echo 'alias ekho="sh ~/.functions/ekho"' >> ~/.bash_profile
source ~/.bash_profile
Now you can call your method from any location for ever ever.
ekho "Wow"
You should not use commands in a test [ ] unless you simulate a variable with $( ) arround the commands. Still not sure SSH will return something to the test. SSH needs the TTY you like connect to, and not the TTY you in at. This will causes problems!
An example without SSH ...
suleiman#antec:~$ if [ "$(cat ~/test.txt)" ]; then echo "Hello World"; else echo "failed"; fi
Hello World
suleiman#antec:~$ if [ "$(cat /this/file/dont/exsist 2>/dev/null)" ]; then echo "Hello World"; else echo "failed"; fi
failed
Addition:
-bash: sc: command not found
This means you have NOT installed the spreadsheet on the host.
This function only making to login in to jump host but not to
secureconsole in to another host from there.
What you trying to do ?
Do you know what SSH does ?
It opens remote TTYs, or with other words: it opens a remote secure console.
You cant run a script and put somewhere a ssh login in it, and then think all code after that will be in the new console, neither will that happen.
You can run ssh on a console, so you get your own TTY and put some commands in it. Or you use ssh in combination with some commands in a script, like
ssh user#host echo "Hello World!"
You can also pass some variables or text though ssh via
echo "Hello World!" | ssh user#host cat
There isnt much more you can do with it and you shouldn't!
I would write this
con.sole() {
if ! ssh -T jumphostname true; then
printf 'Jump host "%s" not available.\n' jumphostname >&2
return 1
fi
sc "$#"
}
The square brace isn't part of the if statement syntax. It is a separate command, the same as test.
Below link would help you to go ahead
ssh username#host_address "command to execute"
For example output:
arul#OA2:~/work/images$ ssh arul#localhost echo "hai"
arul#localhost's password:
hai
arul#OA2:~/work/images$
ssh arul#localhost command will login and "echo hai" command printed in currently logged in prompt"
Citation: https://www.cyberciti.biz/faq/unix-linux-execute-command-using-ssh/
Its because you dont leave a whitespace between the if and the [...
The the correct sintax you want is...
function con.sole
{
if [ ssh jumphostname ]; then
sc $1;
else
echo "host not available"
fi
}
Greetings from Mexico! 🇲🇽
Why are the instructions in an ssh remote execution block evaluated locally on the client side first?
Consider the following code:
ssh -tt serverhostname "
if [ `grep -cm 1 "string" /serverside/file`!= "1" ]; then
echo "Doing some action on" `date`
fi
" 2> /dev/null
One might expect for the instructions listed in the ssh block to be executed on the remote. This is not the case. The if statement is actually executed on the client side. Why? Is there a syntactically correct way to process the instructions server side (on the remote)?
Unquoted and double-quoted arguments are expanded before the command is invoked:
ssh server "echo $HOSTNAME"
is the same as
ssh server "echo clienthostname"
and sends the literal string echo clienthostname to the server. The server therefore writes out the client's hostname.
Single quoted and escaped arguments, meanwhile, are not expanded:
ssh server 'echo $HOSTNAME'
ssh server "echo \$HOSTNAME"
will both send the literal string echo $HOSTNAME to the server, and therefore cause the server to write out the server's hostname.
This applies to all commands, and has nothing to do with ssh.
I asked this question to perhaps help someone else having the same dilemma. You want to execute something on the server, and use the value of that instruction as the basis for something else. But you find the server isn't performing the instructions.
Bash is in fact performing the injected instruction client-side. The only work around I've found is to issue separate commands and have the result store client side. ie.
# Step 1
a=`ssh server grep -cm 1 "something" /serverside/file`
# Step 2
if [ $a != "1" ]; then
ssh -tt server "
echo "perform some series of tasks"
"
fi
I have this script :
#!/bin/bash
./process-list $1
det=$?
echo $det
if [ $det -eq 1 ]
then
echo "!!!"
ssh -n -f 192.0.2.1 "/usr/local/bin/sshfs -r 192.0.2.2:/home/sth/rootcheck_redhat /home/ossl7/r"
rk=$(ssh -n -f 192.0.2.1 'cd /home/s/r/rootcheck-2.4; ./ossec-rootcheck >&2; echo $?' 2>res)
if [ $rk -eq 0 ]
then
echo "not!"
fi
fi
exit;
I ssh to system 192.0.2.1 and run sshfs command on it. actualy I want to mount a directory of system 192.0.2.2 on system 192.0.2.1 and then run a program (which is located in that directory) on system 192.0.2.1. all these ssh and sshfs commands work properly. when I run them manually and output of program ossec-rootcheck is written to file res ,but when I run this script, mount is done but no output is written to file res. I guess program ossec-rootcheck is runned but I don't know why the output isn't written!
this script used to work properly before I don't know what happend suddenly!
As far as I understand the program, the remote machine has stdin>stderr, but how do you get that to the local machine where ssh is being evaluated?
The end ' means on the rk= line, the 2>res happens locally. (and there is no error from ssh, the remote error, if any, is lost when ssh successfully completes.) You could try >res it will get whatever ssh prints out, unfortunately including non-errors.
I am trying to write a shell script that creates some directories on a remote server and then uses scp to copy files from my local machine onto the remote. Here's what I have so far:
ssh -t user#server<<EOT
DEP_ROOT='/home/matthewr/releases'
datestamp=$(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.