Linux – How to set ulimits for a service starting at boot

automationcheflinuxMySQLulimit

I need, for mysql to use large-pages, to set a ulimit – I've done this in limits.conf. However, limits.conf (pam_limits.so), doesn't get read in for init, only for "real" shells. I solved this before by adding a "ulimit -l" to the initscript start function. I need some sort of repeatable way to do this, now that the boxes are managed with chef, and we don't want to take over a file that's actually owned by the RPM.

Best Answer

$ echo "* hard nofile 102400" >> /etc/security/limits.conf
$ echo "* soft nofile 102400" >> /etc/security/limits.conf
$ sysctl -w fs.file-max=102400
$ sysctl -p

The 4 steps can change your system's limits immediately, and can still work after your reboot. You can change the number "102400" to the number of max open-file in your linux system as you want. and

$ sysctl -p

to load in sysctl settings from the file specified or /etc/sysctl.conf if none given.

Related Solutions

How to set ulimits in Solaris 10

On Solaris you can set this parameter to be a hard or soft limit system-wide OR you can do the same for a specific application so that it has the correct number of open file descriptors in its run-time space.

To make it a system-wide change, edit /etc/system with following entries

# Hard limit on file descriptors for single process
set rlim_fd_max = 4096

# Soft limit on the file descriptors for a single process
set rlim_fd_cur = 1024

NOTE: without setting rlim_fd_max as shown above, the default value for file descriptors or nofiles is half of the rlim_fd_cur value. So, it's best to set them both.

If you are using a Solaris project for an application space like Oracle Database, you can set the max file descriptors in the project by:

projadd -U oracle -K “process.max-file-descriptor=(priv,4096,deny)” user.oracle

Additionally, you can set it using ulimit directly in an application's owner's shell startup file. For example, it is possible to establish max file descriptors by setting ulimit in the .profile of the web server's owner to ulimit -s 32768 and calling that from the startup/shutdown script.

As you can see there are lots of options and ways of doing this.

Modify Columns of Large MySQL Tables with Minimal Downtime

I periodically need to make changes to tables in mysql 5.1, mostly adding columns.

Don't. No really. Just don't. It should be a very rare occasion when this is ever necessary.

Assuming your data really is normalized to start with, the right way to solve the problem is to add a new table with a 1:1 relationship to the base table (non-obligatory on the new table).

Having to add columns regularly is usually an indicator of a database which is not normalized - if your schema is not normalized then that's the problem you need to fix.

Finally, if your schema really, really is normalized and you really, really must keep adding columns then:

Ensure you've got a timestamp column on the database or that it is generating replication logs
Create a copy (B) of the table (A)
add the new columns to B (this will still block with myisam)
disable transactions
rename the original table (A) as something else (backup)
rename the new table (B) with the name of the original table (A)
replay the transactions from the start of the operation from the replication log or from the backup table
enable transactions.

Best Answer

Related Solutions

How to set ulimits in Solaris 10

Modify Columns of Large MySQL Tables with Minimal Downtime

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