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Setting macOS system limits.md
The following shows how to increase the `maxfiles` (maximum number of open files) soft limit, but the same process can be applied to any system limit. On Linux these are set using `sysctl`. # Increasing per-process (launchd) If an individual `launchd` process needs a higher soft limit, adding the following to its `.plist` will do nicely: ```xml <key>SoftResourceLimits</key> <dict> <key>NumberOfFiles</key> <integer>10240</integer> </dict> ``` Of course, this may fall apart if the `.plist` can be restored to its default version by a software update. Cunning Plan™: Create a LaunchDaemon or cron job to run a script every night that checks the `.plist` and inserts the above if it’s not there (easy to do using XMLStarlet), then restarts the relevant daemon. # Increasing globally Too low a value of `maxfiles` can cause things like `mysqldump` to fail (no backups for you, although MariaDB seems to set it independently these days). To show the current limit (probably stupidly low, e.g., 256): ```sh launchctl limit maxfiles ``` To set temporarily: ```sh sudo launchctl limit maxfiles 10240 2147483647 ``` The third and fourth arguments are the soft and hard limits, respectively. Always set the fourth argument to 2147483647 (= `INT_MAX` = “unlimited”) unless you really want your machine to grind to a halt (https://apple.stackexchange.com/a/366319)! As per the `launchctl` man page (emphasis added): “When a given resource is specified, it prints the limits for that resource. With a third argument, it sets both the hard and soft limits to that value. With four arguments, the third and forth [sic] argument represent the soft and hard limits respectively.” To set more persistently (https://superuser.com/a/1171028), create `/Library/LaunchDaemons/limit.maxfiles.plist` with the following contents: ```xml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Label</key> <string>limit.maxfiles</string> <key>ProgramArguments</key> <array> <string>launchctl</string> <string>limit</string> <string>maxfiles</string> <string>10240</string> <string>2147483647</string> </array> <key>RunAtLoad</key> <true/> <key>ServiceIPC</key> <false/> </dict> </plist> ``` However, note that this only occurs somewhere during the startup sequence, not first, so servers (e.g., MySQL) may start earlier and therefore need to be restarted in order to inherit the new value. # Checking To check the open files limit in MySQL: ```sql select @@open_files_limit; ``` The following shows how to increase the `maxfiles` (maximum number of open files) soft limit, but the same process can be applied to any system limit. On Linux these are set using `sysctl`. # Increasing per-process (launchd) If an individual `launchd` process needs a higher soft limit, adding the following to its `.plist` will do nicely: ```xml <key>SoftResourceLimits</key> <dict> <key>NumberOfFiles</key> <integer>10240</integer> </dict> ``` Of course, this may fall apart if the `.plist` can be restored to its default version by a software update. Cunning Plan™: Create a LaunchDaemon or cron job to run a script every night that checks the `.plist` and inserts the above if it’s not there (easy to do using XMLStarlet), then restarts the relevant daemon. # Increasing globally Too low a value of `maxfiles` can cause things like `mysqldump` to fail (no backups for you). To show the current limit (~~probably stupidly low, e.g., 256~~ this now seems to be set automatically): ```sh launchctl limit maxfiles ``` To set temporarily: ```sh sudo launchctl limit maxfiles 10240 2147483647 ``` The third and fourth arguments are the soft and hard limits, respectively. Always set the fourth argument to 2147483647 (= `INT_MAX` = “unlimited”) unless you really want your machine to grind to a halt (https://apple.stackexchange.com/a/366319)! As per the `launchctl` man page (emphasis added): “When a given resource is specified, it prints the limits for that resource. With a third argument, it sets both the hard and soft limits to that value. With four arguments, the third and forth [sic] argument represent the soft and hard limits respectively.” To set more persistently (https://superuser.com/a/1171028), create `/Library/LaunchDaemons/limit.maxfiles.plist` with the following contents: ```xml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Label</key> <string>limit.maxfiles</string> <key>ProgramArguments</key> <array> <string>launchctl</string> <string>limit</string> <string>maxfiles</string> <string>10240</string> <string>2147483647</string> </array> <key>RunAtLoad</key> <true/> <key>ServiceIPC</key> <false/> </dict> </plist> ``` However, note that this only occurs somewhere during the startup sequence, not first, so servers (e.g., MySQL) may start earlier and therefore need to be restarted in order to inherit the new value. # Checking To check the open files limit in MySQL: ```sql select @@open_files_limit; ```

Setting macOS system limits.md

The following shows how to increase the `maxfiles` (maximum number of open files) soft limit, but the same process can be applied to any system limit. On Linux these are set using `sysctl`.

# Increasing per-process (launchd)

If an individual `launchd` process needs a higher soft limit, adding the following to its `.plist` will do nicely:

```xml
    <key>SoftResourceLimits</key>
        <dict>
            <key>NumberOfFiles</key>
            <integer>10240</integer>
        </dict>
```

Of course, this may fall apart if the `.plist` can be restored to its default version by a software update.

Cunning Plan™: Create a LaunchDaemon or cron job to run a script every night that checks the `.plist` and inserts the above if it’s not there (easy to do using XMLStarlet), then restarts the relevant daemon.

# Increasing globally

Too low a value of `maxfiles` can cause things like `mysqldump` to fail (no backups for you, although MariaDB seems to set it independently these days). To show the current limit (probably stupidly low, e.g., 256):

```sh
launchctl limit maxfiles
```

To set temporarily:

```sh
sudo launchctl limit maxfiles 10240 2147483647
```

The third and fourth arguments are the soft and hard limits, respectively. **Always** set the fourth argument to 2147483647 (= `INT_MAX` = “unlimited”) unless you really want your machine to grind to a halt (https://apple.stackexchange.com/a/366319)! As per the `launchctl` man page (emphasis added):

“When a given resource is specified, it prints the limits for that resource. **With a third argument, it sets both the hard and soft limits to that value.** With four arguments, the third and forth *[sic]* argument represent the soft and hard limits respectively.”

To set more persistently (https://superuser.com/a/1171028), create `/Library/LaunchDaemons/limit.maxfiles.plist` with the following contents:

```xml
<?xml version="1.0" encoding="UTF-8"?>  
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"  
        "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">  
  <dict>
    <key>Label</key>
    <string>limit.maxfiles</string>
    <key>ProgramArguments</key>
    <array>
      <string>launchctl</string>
      <string>limit</string>
      <string>maxfiles</string>
      <string>10240</string>
      <string>2147483647</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>ServiceIPC</key>
    <false/>
  </dict>
</plist> 
```

However, note that this only occurs *somewhere* during the startup sequence, not first, so servers (e.g., MySQL) may start earlier and therefore need to be restarted in order to inherit the new value.

# Checking

To check the open files limit in MySQL:

```sql
select @@open_files_limit;
```