add mdconfig
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# FreeBSD
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#wip #🐇 #notnow
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#wip #🐇 #notnow #bsd
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FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms. A large community has continually developed it for more than thirty years. Its advanced networking, security, and storage features (using [ZFS](../linux/filesystems/ZFS.md) natively) have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.
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# pkg
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Pkg is the Package Manager on BSDs
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## pkg
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Pkg is the Package Manager on BSDs
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#refactor -> add pkg usage
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## mdconfig
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`mdconfig` lets you create and control memory disks.
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Usage: `mdconfig [OPTIONS]`
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`mdconfig file` is provided for convenience as an abbreviation of `mdconfig -a -t vnode -f file`.
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### Options
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| Option | Description |
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| --------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `-a` | Attach a memory disk. This will configure and attach a memory disk with the parameters specified and attach it to the system. If the `-u unit` option is not provided, the newly created device name will be printed to stdout |
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| `-d` | Detach a memory disk from the system and release all resources |
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| `-r` | Resize a memory disk |
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| `-t type` | Select the type of the memory disk:<br>- `malloc`: Storage for this type of memory disk is allocated with malloc<br>- `vnode`: A file specified with `-f file` becomes the backing store for this memory disk<br>- `swap`: Storage for this type of memory disk is allocated from buffer memory. Pages get pushed out to swap when the system is under memory pressure. Using is generally preferred over `malloc`<br>- `null`: Bitsink, all writes do nothing, all reads return zero |
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| `-f file` | Filename to use for the vnode type memory disk |
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| `-l` | List configured devices. Use with `-u` or `-v` for more details |
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| `-n` | When printing md device names, print only the unit number without the md prefix |
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| `-s size` | Size of the memory disk |
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| `-S sectorsize` | Sectorsize to use for the memory disk |
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| `-L label` | Associate a label with the new memory disk |
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| -o OPTION | **\[no]option**: Set or reset options. <br><br> **\[no]async**: For vnode backed devices: avoid `IO_SYNC` for increased performance but at the risk of deadlocking the entire kernel. <br><br> **\[no]cache**: For vnode backed devices: enable/disable caching of data in system caches. The default is to not cache. Accesses via the device are converted to accesses via the vnode. The caching policy for the vnode is used initially. This is normally to cache. This caching policy is retained if the cache option is used. Otherwise, caching is limited by releasing data from caches soon after each access. The release has the same semantics as the `POSIX_FADV_DONTNEED` feature of posix_fadvise. The result is that with normal (non-zfs) caching, buffers are released from the buffer cache soon after they are constructed, but their data is kept in the page cache at lower priority. The cache option tends to waste memory by giving unwanted double caching, but it saves time if there is memory to spare. <br><br> **\[no]reserve**: Allocate and reserve all needed storage from the start, rather than as needed. <br><br> **\[no]cluster**: Enable clustering on this disk. <br><br> **\[no]compress**: Enable/disable compression features to reduce memory usage. <br><br> **\[no]force**: Disable/enable extra sanity checks to prevent the user from doing something that might adversely affect the system. This can be used with the `-d` flag to forcibly destroy an md disk that is still in use. <br><br> **\[no]mustdealloc**: For vnode backed devices: detect whether hole-punching is supported by the underlying file system. If the file system supports hole-punching, then to handle a `BIO_DELETE` request, some or all of the request's operation range may be turned into a hole in the file used for backing store. Any parts which are not turned into holes are zero-filled in the file. If the file system does not support hole-punching, `BIO_DELETE` requests to the device are not handled and will fail with `EOPNOTSUPP`. When mustdealloc is not specified or \[no]mustdealloc is specified, for a `BIO_DELETE` request, if the file system supports hole-punching, some or all of the request's operation range may be turned into a hole in the file used for backing store. Any parts which are not turned into holes are zero-filled in the file. If the file system of the vnode type memory disk does not support hole-punching, the request's operation range is zero-filled in the file. <br><br> **\[no]readonly**: Enable/disable readonly mode. <br><br> **\[no]verify**: For vnode backed devices: enable/disable requesting verification of the file used for backing store. The type of verification depends on which security features are available. One example of verification is testing file integrity with checksums or cryptographic signatures. |
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| -u unit | Request a specific unit number or device name for the md device instead of automatic allocation. If a device name is specified, it must start with "md" followed by the unit number. |
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### Examples
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Create a disk with `/tmp/boot.flp` as backing storage. The name of the allocated unit will be printed on stdout, such as "md0":
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```shell
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mdconfig /tmp/boot.flp
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```
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Create a 1 gigabyte swap backed memory disk named "md3":
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```shell
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mdconfig -s 1g -u md3
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```
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Detach and free all resources used by `/dev/md3`:
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```shell
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mdconfig -du md3
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```
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Show detailed information on current memory disks:
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```shell
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mdconfig -lv
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```
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Resize the "md3" memory disk to 2 gigabytes:
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```shell
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mdconfig -rs 2g -u md3
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```
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Create a 1 gigabyte swap backed disk, initialize an ffs file system on it, and mount it on `/tmp`:
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```shell
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mdconfig -s 1g -u md10
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newfs -U /dev/md10
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mount /dev/md10 /tmp
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chmod 1777 /tmp
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```
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Create a memory disk out of an ISO 9660 CD image file, using the first available md device, and then mount it:
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```shell
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mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
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```
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Create a file-backed device from a hard disk image that begins with 512K of raw header information. gnop is used to skip over the header information, positioning md1.nop to the start of the filesystem in the image.
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```shell
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mdconfig -u md1 -f diskimage.img
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gnop create -o 512K md1
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mount /dev/md1.nop /mnt
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```
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