User limit in linux

limits.conf File To Limit Users, Process In Linux With Examples

limits.conf configuration file is used to limit user, domain, process-related metrics. Limits.conf is related to pam_limits module.

limits.conf Configuration File

There is a configuration file named limits.conf and located at /etc/security/ . The default content of this file is as below. We can see that there are different columns named domain , type , item and value .

As we can see all configurations are commented so they are not effective. There is also a directory which is use to store configuration files in a separate files to maintain easily. This location is /etc/security/limits.d/ . It is by default empty but we can create rules in this directory easily.

limits.conf Syntax

Limits.conf file have a simple and reliable syntax. This syntax is defined to easily set context, type, limits and related values. We will look all of this terms below.

Domain

While limits configuration we need to specify context. This content can be defined in various ways and various parameters. The first column of the rule is the domain. A domain can be one of the following value.

• username
• groupname
• * specifies all
• userid
• groupid

While limiting there is two type of limit implementation. These are called hard and soft . Hard limits are set by root and enforced by kernel. The hard limits can not be exceeded. Soft limits have some range overload. But the overload can be for a little time and can not continue forever.

Items are the core of limits. Items are used to specify the item the limit will be applied. For example, if we want to limit the maximum process number we will use nproc numbers. Here are some of the items that can be used to for limit operation.

• fsize specifies maximum file size
• nofile specifies maximum number of file size
• cpu specifies maximum CPU time
• nproc specifies maximum number of process
• maxlogins specifies maximum number of logins
• maxsyslogins specifies maximum number of logins for all users

Specify User For Limit

Now we can start with examples. As we stated we can limit relevant items according to the user name. In the following rule, we will specify a limit for username ismail where we specify the user name in the first column.

In this example we set core or CPU limit for value 1000000 for username ismail as hard

Specify Group For Limit

In this example, we can specify the limit for a user group name. This type of limitation can be useful if we want to restrict some user group names.

In this example we specify apache group name to limit process number as maximum 20

Use Wildcard For Limit

While specifying the domain or the users and groups we may need to set limits for all users and groups in a system. Here we will use * or a wildcard for this.

In this example we set rss limit for all users and groups in this systems.

Specify User ID Range For Limit

We want to specify limit some users. But they are not in a user group and we do not want or can create groups for these groups. Specifying limits one by one is a problem. We can specify multiple users like below. But the restriction is that we will specify the range.

The rule above will be applied to the users those User ID’s are between 1000 and 1010 . The : operator used to specify the range.

Specify Group ID Range For Limit

The similar definition like previous user range is group range. We will specify group ID range like below.

In this example, the rules will be applied for the group ID between 500 and 510. We use @ operator to specify ID’s as a group and : for range.

Limit Number of Process

Now we will start to look at different item types to use. There are more items than described here but these are the most popular ones. The first example is limiting the number of processes for a user.

In the example, we limit the process number with nproc item. The user the rule will apply is ismail and the maximum number of the process for this user can own is 20

Limit CPU Time

Another useful item to limit is CPU time. We can set limits about the CPU time .

In this example we applied maximum 10000 cycles for user ismail by using cpu item.

Limit Number Of Open File

We can limit the numbers of files a user can open in time. This can be useful to prevent disk bottlenecks if the system has a lot of users those access files.

In this example we specify that the user ismail can only open 512 files or file descriptors with nofile item.

Limit Number Of Logins

By default, a user can have infinite numbers of connections, sessions, or logins in a system. This may create some security or performance problems for the systems. We can set some limits on this.

In these examples, we limit the student group’s user’s login count. We use maxlogins for each user in the student group. The maximum number of login can not be more than 4 .

Limit Number Of System Logins

In the previous example, we have restricted maximum logins as a user base. we can also specify the total number of logins in system-wide. This restriction will be effective in a general manner.

In this example, we restrict all users and groups but actually, this is not a user or group based restriction. We set this rule system-wide and use maxsyslogin item as 40

Limit Maximum File Size

We may want to restrict file size. This restriction can be useful in temp or similar usage type files.

In this example, we limit the student’s single file size as 4000000 . This is a presentation of KB or kilobyte. So the example means 4 GB . We use fsize as item type.

Источник

How to Set Limits on User Running Processes in Linux

One of the Linux’s beauties is that you can control almost everything about it. This gives a system administrator a great control over his system and better utilization of the system resources.

While some might have never thought about doing this, it is important to know that in Linux you can limit how much resource a single user may use and for how long.

In this short topic, we will show you how to limit the number of processes started by user and how to check the current limits and modify them.

Before we go any further there are two things we need to point:

1. You need root access to your system to modify the user limits
2. You must be extremely careful if you plan to modify these limits

To setup user limits, we will need to edit the following file:

This file is used to apply ulimit created by the pam_module.

The file has the following syntax:

Here we will stop to discuss each of the options:

• Domain – this includes usernames, groups, guid ranges etc
• Type – soft and hard limits
• Item – the item that will be limited – core size, file size, nproc etc
• Value – this is the value for the given limit

A good sample for a limit is:

The above line sets a hard limit of maximum 20 processes on the «student» group.

If you want to see the limits of a certain process has you can simply “cat” the limits file like this:

Where PID is the actual process ID, you can find out process id by using ps command. For more detailed explanation, read our article that says – Find Running Linux Processes and Set Process Limits Per-User Level

So here is an example:

Sample Output

All of the lines are pretty much self explanatory. However if you want to find more the settings you can input in limits.conf file, you can have a look at the manual provided here.

If you have any questions or comments, please do not hesitate to submit them in the comment section below.

If You Appreciate What We Do Here On TecMint, You Should Consider:

TecMint is the fastest growing and most trusted community site for any kind of Linux Articles, Guides and Books on the web. Millions of people visit TecMint! to search or browse the thousands of published articles available FREELY to all.

If you like what you are reading, please consider buying us a coffee ( or 2 ) as a token of appreciation.

We are thankful for your never ending support.

Источник

How to Limit Process at User Level on Linux

When the system is heavily used, it would be a big challenge for system administrators to manage resources. Ulimit (user limit) is a powerful command which helps to limit resources on your system.

Sometime, but not very often a single user may start too many processes to make the system unstable. To mitigate this we can use ulimit command to limit the number process each user or group can run.

In this tutorial, we learn how to limit the process at user level on Linux.

With ulimit you can set two kinds of limits:

• Hard limit: This limit is for security purpose. Hard limit can be increased only done by root (ie a non root process cannot go above a hard limit)
• Soft limit: This limit can be changed by process at any time. A non user can set a limit between (0 and hard limit) for its processes.

Check all current limits

You can check all the limits for the currently logined user.

Run the following ulimit command with -a option:

You can see that there are some unlimited settings. These limits can be changed.

Note: The /proc file-system stores the per-process limits in the file system object located at /proc/4548/limits , where ‘4548’ is the process’s PID or process identifier.

Set ulimit for user

You can use ulimit -u to find max user processes or nproc limit.

You can change max user processes by the following command:

If you get any error or unable to change check if you have set any limits in ‘/etc/security/limits.conf’.

Limits can be set for specific user or group in limits.con file.

If you want to set ‘infrateam’ to have more process than ‘testers’ and limit user bob nproc to ’60’, then set as follows:

Here we set limit to open files using ‘nofile’ field. As we set soft limit, user will get warnings when they reach the lower limit.

Set Ulimit for open file

We can use ulimit command to view the limits open files for each user.

Check the user level open file hard limit

Check the user level open file soft limit

If you want to change the current open file limits (soft or hard) you can update in ‘limits.conf’ file.

In our example, we will set the maximum number of files to 16384 for all users of the system.

Reboot your machine and test the new limits configuration

To check Linux system-wide current maximum number of open file, then run the following command:

To change maximum number of open file run following commands:

to make it persistent after reboot update in ‘sysctl.conf’ file

Set user limit via systemd

Earlier we discussed that we can set limits by editing the /etc/security/limits.conf file but systemd would ignore this file.

Systemd by default reads from ‘/etc/systemd/system.conf’ file. Below are systemd limits equivalent to ulimits.

You can set user limit by editing the /etc/systemd/user.conf file.

For example, you can try as below:

Some services that are started via systemd ignore the /etc/security/limits.conf file. To face this issue, you should set the limits in the service definition file.

You need to update the service file as following:

Conclusion

In this tutorial, we learned how to use ulimit command to set limit for processes for a user. I hope you enjoyed reading and please leave your suggestions or feedback in the comment section.

Источник

Setting Limits for Users in Linux

session required /lib/security/pam_limits.so.

[username or @groupname] [type resource] [limit]

Author : LazySystemAdmin

Share this

Related Posts

4 comments

great yaar . super i need help on monitoring the server , can you please help me out.

Sure.. Reach out me in email

Hi Prathiban this is very useful post; I need to allocated and restrict an organization and the users in in it using the hard disk space in the business scenario can you help me in this regard.

You need to use disk quota. Check out this.

What do you think about this Article? Add your Opinion. Emoticon Emoticon

Labels

Browse All Articles

• ►2018 (3)
  • ►December (1)
  • ►May (1)
  • ►January (1)

• ►2017 (2)
  • ►November (1)
  • ►February (1)

• ►2014 (2)
  • ►November (1)
  • ►February (1)

• ►2013 (3)
  • ►August (1)
  • ►January (2)

• ▼2012 (14)
  • ►September (1)
  • ▼August (6)
    • Allow SSH and Web Connections in IP Tables in Linux
    • migratepv VS replacepv
    • What is umask?
    • Changing default gateway in SuSE Linux
    • Setting Limits for Users in Linux
    • Special Shell Variables — Useful for Scripting
  • ►June (1)
  • ►May (1)
  • ►April (1)
  • ►February (2)
  • ►January (2)

• ►2011 (98)
  • ►December (1)
  • ►November (2)
  • ►September (6)
  • ►July (17)
  • ►June (3)
  • ►May (14)
  • ►April (12)
  • ►March (15)
  • ►February (21)
  • ►January (7)

• ►2010 (165)
  • ►December (5)
  • ►October (13)
  • ►September (12)
  • ►August (13)
  • ►July (15)
  • ►June (26)
  • ►May (21)
  • ►April (25)
  • ►March (19)
  • ►February (2)
  • ►January (14)

• ►2009 (45)
  • ►December (23)
  • ►November (18)
  • ►September (1)
  • ►August (3)

• ►2008 (1)
  • ►November (1)

Popular Articles

About LazySystemAdmin

LazySystemAdmin is a site with 300+ Articles, how-to guides and video tutorials on all things related to System Administration and Technology. This Blog is to share our knowledge and expertise on System Administration and Operating Systems. Stay connected with LazySystemAdmin.

Источник