I would like to get the jobid from procfs in Linux. I see only Pid , Ppid in the /proc//status files. But I needed jobid too. Please let me know if there is a way to get the info.
Thanks !
If you're referring to the job IDs in the shell, this information is known only to the shell that created the job. The kernel has no concept of 'job IDs' and therefore does not track them, or expose them via procfs (or any other method).
Related
Please help.
So, I'm given a task to monitor a particular process in CentOS.
There are certain requirements.
Can't monitor using PID, because once process is killed or dead, solution is of no use.
It'll be great if I could know how much is the consumption of each thread of a process.
I've researched enough but with no success.
Thanks in advance.
I am uncertain what exactly you are trying to achieve, but this is how I would proceed:
Suggested Approaches
Multiple Process IDs per process name
top -H -p $(pgrep <process_name> | paste -s -d, -)
Single Process ID per process name
top -H -p $(pgrep <process_name>)
Further reading
Reuse command output
Thread Monitoring with top
Turn stdout into comma-separated string
Suggestion
Maybe think about implementing a solution like Prometheus with Node Exporter or Zabbix or Nagios.
for my Computing Controlled Assessment I am looking into some of the basic commands for the Linux OS Debian. For the final question I have to write a short essay on using the top command along with ps and kill to investigate misbehaving system. The question asks to use help from PC specialists (or just any experienced Debian users). So if anyone could give any information on how a specialist could use these commands and anything helpful in general on these commands. Remember I'm here for information and not an answer. Thanks
top is used for displaying a list of processes, and by default, is sorted by the amount of CPU usage it's using - so in your case, it's a handy tool to see if a specific process is taking up most of the CPU usage and causing the system to run slower. It also displays the process ID (PID) as well as the user running it. Think of it like the Linux equivalent of Task Manager in Windows.
ps is similar to top, but instead of constantly refreshing, it spews out all of the current processes running on the server, as well as the PID (important). Usually this is used as ps aux, or to be more specfic you could use this with grep to search for a specific process, e.g. ps aux | grep httpd to display the current Apache processes running.
kill is used to kill process running on the system, so if you had a script on the system taking up most of the resources and you want to forcefully kill the process, you'd use kill. You can also use the killall command to kill all processes with a matching string, e.g. killall httpd.
The steps I'd take to investigate a misbehaving system would be to:
1) Use top or ps to locate the process taking up the most resources, and remember the process ID.
2) If I wanted to kill the process, I'd use: kill <process ID>.
If you need anything else clarifying or explaining - feel free to comment!
EDIT: https://serverfault.com/ - This may be the best place to post future questions like this.
Best way to learn about this commands is to read man (manual) pages. To discover information about top just type:
$ man top
in command line and enjoy. Similarly you can display man pages for most unit command line tools using:
$ man <command>
on linux can I show a process's detail including what command/script started it, etc?
top is show all processes and I wish to get more information on a process using its id
ps -p <pid> -lF
...will give you information about the process like which command started it, time it was started, its state, parent pid, size etc.
If you can tell in more detail as what all information you want to know about process from pid, then we can help you better.
You can find lots of information in /proc/{PID} directories.
I am very new to linux and am sorry for the newbie questions.
I had a homework extra credit question that I was trying to do but failed to get it.
Q. Write a security shell script that logs the following information
for every process: User ID, time started, time ended (0 if process is
still running), whether the process has tried to access a secure file
(stored as either yes or no) The log created is called
process_security_log where each of the above pieces of information is
stored on a separate line and each entry follows immediately (that is,
there are no blank lines). Write a shell script that will examine
this log and output the User ID of any process that is still running
that has tried to access a secure file.
I started by trying to just capturing the User and echo it but failed.
output=`ps -ef | grep [*]`
set -- $output
User=$1
echo $User
The output of ps is both insufficient and incapable of producing data required by this question.
You need something like auditd, SELinux, or straight up kernel hacks (ie. fork.c) to do anything remotely in the realm of security logging.
Update
Others have made suggestions to use shell command logging, ps and friends (proc or sysfs). They can be useful, and do have their place (obviously). I would argue that they shouldn't be relied on for this purpose, especially in an educational context.
... whether the process has tried to access a secure file (stored as either yes or no)
Seems to be the one that the other answers are ignoring. I stand by my original answer, but as Daniel points out there are other interesting ways to garnish this data.
systemtap
pref
LTTng
For an educational exercise these tools will help provide a more complete answer.
Since this is homework, I'm assuming that the scenario isn't a real-world scenario, and is merely a learning exercise. The shell is not really the right place to do security auditing or process accounting. However, here are some pointers that may help you discover what you can do at the shell prompt.
You might set the bash PROMPT_COMMAND to do your process logging.
You can tail or grep your command history for use in logging.
You can use /usr/bin/script (usually found in the bsdutils package) to create a typescript of your session.
You can run ps in a loop, using subshells or the watch utility, to see what processes are currently running.
You can use pidof or pgrep to find processes more easily.
You can modify your .bashrc or other shell startup file to set up your environment or start your logging tools.
As a starting point, you might begin with something trivial like this:
$ export PROMPT_COMMAND='history | tail -n1'
56 export PROMPT_COMMAND='history | tail -n1'
$ ls /etc/passwd
/etc/passwd
57 ls /etc/passwd
and build in any additional logging data or process information that you think necessary. Hope that gets you pointed in the right direction!
Take a look at the /proc pseudo-filesystem.
Inside of this, there is a subdirectory for every process that is currently running - process [pid] has its information available in /proc/[pid]/. Inside of that directory, you might make use of /prod/[pid]/stat/ or /proc/[pid]/status to get information about which user started the process and when.
I'm not sure what the assignment means by a "secure file," but if you have some way of determining which files are secure, you get get information about open files (including their names) through /prod/[pid]/fd/ and /prod/[pid]/fdinfo.
Is /proc enough for true security logging? No, but /proc is enough to get information about which processes are currently running on the system, which is probably what you need for a homework assignment about shell scripting. Also, outside of this class you'll probably find /proc useful later for other purposes, such as seeing the mapped pages for a process. This can come in handy if you're writing a stack trace utility or want to know how they work, or if you're debugging code that uses memory-mapped files.
How could I check the state of a Linux threads using codes, not tools? I want to know if a thread is running, blocked on a lock, or asleep for some other reason. I know the Linux tool "top" could do this work. But how to implement it in my own codes. Thanks.
I think you should study in details the /proc file system, also documented here, inside kernel source tree.
It is the way the Linux kernel tells things to outside!
There is a libproc also (used by ps and top, which reads /proc/ pseudo-files).
See this question, related to yours.
Reading files under /proc/ don't do any disk I/O (because /proc/ is a pseudo file system), so goes fast.
Lets say your process id is 100.
Go to /proc/100/task directory and there you could see multiple directories representing each threads.
then inside each subdirectory e.g. /proc/100/task/10100 there is a file named status.
the 2nd line inside this file is the state information of the thread.
You could also find it with by looking at the cgroup hierarchy of the service that your process belongs. Cgroups have a file called "tasks" and this file lists all the tasks of a service.
For example:
cat /sys/fs/cgroup/systemd/system.slice/hello.service/tasks
Note: cgroup should be enabled in your linux kernel.