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Diffstat (limited to 'udev-config/doc/60-persistent-storage.txt')
| -rw-r--r-- | udev-config/doc/60-persistent-storage.txt | 95 |
1 files changed, 0 insertions, 95 deletions
diff --git a/udev-config/doc/60-persistent-storage.txt b/udev-config/doc/60-persistent-storage.txt deleted file mode 100644 index 32062c559..000000000 --- a/udev-config/doc/60-persistent-storage.txt +++ /dev/null @@ -1,95 +0,0 @@ -Purpose of rules file: - -This rules file provides nonvolatile, unique names (in the form of symlinks) -for various types of storage devices -- both IDE/ATA and SCSI. - - -Description of rules: - -First, similar to the 60-persistent-input.rules file, we skip the entire file -for uevents that this rules file should not apply to, as an optimization. The -file does not apply to removal uevents or non-block devices. It does not apply -to ramdisks, loopback-mount devices, floppy disks, netblock devices, or device- -mapper devices. It also should not apply to removable devices (that is, non- -partition devices with attributes named "removable" with the value "1", or -partition devices whose parents have "removable" set to "1" -- partition -kobjects don't have the "removable" attribute, only whole-disk kobjects do). - -For partition devices, we use the IMPORT{parent} option to pull in all the -environment variables that get set for the parent device. (The parent of a -partition device is the containing whole-disk device.) The IMPORT{parent} -option is documented in the udev(7) manpage, but basically the value that we -assign is used as a filter of environment variable names to import. - -Now, we start with rules to create by-ID symlinks (similar to the by-ID links -created for input devices). For hd* whole-disk devices (they're IDE/ATA, since -they start with hd), we run the ata_id program in --export mode. The ata_id -program requires a device node to be passed, so we also use the $tempnode Udev -variable -- this causes Udev to create a temporary device node somewhere and -substitute its name where $tempnode appears in the program command line. - -The ata_id program, in --export mode, prints several ID_* values. If we're -looking at a whole-disk device, and if ID_SERIAL is among those, we add a -symlink containing the device's ID_MODEL and ID_SERIAL values. If we're -looking at a partition device, we create an ID_MODEL- and ID_SERIAL-based -symlink also, but we add -partX to the end of the link name (where X is the -partition number). - -For SCSI devices, we first make some modifications to the environment. If the -device's kobject has a parent with a non-empty "ieee1394_id" attribute, then -the device is Firewire, so we set the ID_SERIAL environment variable to the -value of that attribute, and we set ID_BUS to "ieee1394". Now, if ID_SERIAL is -not set, we run usb_id, which (if this is a USB storage device) will print -various values. If ID_SERIAL is still unset, we run scsi_id with a set of -parameters designed to get an ID_SERIAL by querying the device itself. If that -still fails, we try running scsi_id in a mode that prints the information even -if the disk doesn't support so-called "vital product data" pages. If the -uevent is for a DASD device, we run dasd_id. - -If one of these *_id programs gave us an ID_SERIAL, then for whole-disk devices -we create a by-ID symlink using the ID_BUS and ID_SERIAL. For partition -devices, we create a by-ID symlink that has the same form except we add -partX -to the end (just like for IDE/ATA devices). - - -Now we have some rules to create by-path persistent symlinks. We start by -running the path_id program on the DEVPATH (%p) value. For whole-disk devices -and SCSI ROM type devices, we create a symlink directly, using the environment -variable ID_PATH, under the /dev/disk/by-path directory. But for SCSI tape -devices, we create a by-path symlink in the /dev/tape/by-path directory (we -base the symlink on the same information, though: the ID_PATH value printed by -path_id). Now, for both SCSI ROM and SCSI tape devices, we skip everything -that's left in the rules file (this is another optimization: neither SCSI ROM -nor SCSI tape devices have UUIDs, labels, or EDD information). - -For partition devices, we now create a by-path symlink of the same form as the -other partition device persistent symlinks (that is, with the same name as the -parent device, but with -partX added). We know that ID_PATH is set whenever it -applies, because we ran the path_id program on the parent device, and we did an -IMPORT{parent} on ID_* earlier in the rules file. - -Now we create by-label and by-uuid symlinks. These use properties of various -filesystems to generate a persistent name for a partition. For instance, if -you use the ext2 filesystem, you can use e2label to assign a label, and mke2fs -assigns a UUID when the filesystem is created. MS-DOS compatible filesystems -also assign a "UUID" (actually it's just a serial number, created based on the -date and time the partition was formatted, so it is not unique), which these -rules will also use. But for removable partitions, we skip the rules (for the -same reason as we skipped them above for removable disks). - -We run the vol_id program to get ID_FS_USAGE, ID_FS_UUID, and ID_FS_LABEL_SAFE -values. (vol_id supports other values as well, but we do not use them here.) -ID_FS_USAGE corresponds to the way the filesystem is supposed to be used; if it -gets set to "filesystem", "other", or "crypto", we create a symlink. If -ID_FS_UUID is set, we use it in a by-uuid symlink. If ID_FS_LABEL_SAFE is set, -we use it in a by-label symlink. - -Finally, we create EDD-based symlinks in the by-id directory. For whole-disk -devices, we run edd_id to get the EDD-generated ID string. (For partition -devices, we import this string from the parent.) If edd_id yields an ID_EDD -value, we use it in a symlink, for both whole disks and partitions. - - -The last rule in the file is merely a LABEL that various other rules use to -bypass the file (or the rest of the file) when needed. - |