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104 lines
3.1 KiB
104 lines
3.1 KiB
2 years ago
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// -*- mode:doc; -*-
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// vim: set syntax=asciidoc:
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[[makedev-syntax]]
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== Makedev syntax documentation
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The makedev syntax is used in several places in Buildroot to
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define changes to be made for permissions, or which device files to
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create and how to create them, in order to avoid calls to mknod.
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This syntax is derived from the makedev utility, and more complete
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documentation can be found in the +package/makedevs/README+ file.
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It takes the form of a space separated list of fields, one file per
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line; the fields are:
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|===========================================================
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|name |type |mode |uid |gid |major |minor |start |inc |count
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|===========================================================
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There are a few non-trivial blocks:
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- +name+ is the path to the file you want to create/modify
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- +type+ is the type of the file, being one of:
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* f: a regular file
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* d: a directory
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* r: a directory recursively
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* c: a character device file
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* b: a block device file
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* p: a named pipe
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- +mode+ are the usual permissions settings (only numerical values
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are allowed)
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- +uid+ and +gid+ are the UID and GID to set on this file; can be
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either numerical values or actual names
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- +major+ and +minor+ are here for device files, set to +-+ for other
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files
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- +start+, +inc+ and +count+ are for when you want to create a batch
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of files, and can be reduced to a loop, beginning at +start+,
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incrementing its counter by +inc+ until it reaches +count+
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Let's say you want to change the permissions of a given file; using
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this syntax, you will need to write:
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----
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/usr/bin/foo f 755 0 0 - - - - -
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/usr/bin/bar f 755 root root - - - - -
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/data/buz f 644 buz-user buz-group - - - - -
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----
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Alternatively, if you want to change owner/permission of a directory
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recursively, you can write (to set UID to foo, GID to bar and access
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rights to rwxr-x--- for the directory /usr/share/myapp and all files
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and directories below it):
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----
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/usr/share/myapp r 750 foo bar - - - - -
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----
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On the other hand, if you want to create the device file +/dev/hda+
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and the corresponding 15 files for the partitions, you will need for
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+/dev/hda+:
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----
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/dev/hda b 640 root root 3 0 0 0 -
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----
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and then for device files corresponding to the partitions of
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+/dev/hda+, +/dev/hdaX+, +X+ ranging from 1 to 15:
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----
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/dev/hda b 640 root root 3 1 1 1 15
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----
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Extended attributes are supported if
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+BR2_ROOTFS_DEVICE_TABLE_SUPPORTS_EXTENDED_ATTRIBUTES+ is enabled.
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This is done by adding a line starting with +|xattr+ after
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the line describing the file. Right now, only capability
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is supported as extended attribute.
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|=====================
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| \|xattr | capability
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|=====================
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- +|xattr+ is a "flag" that indicate an extended attribute
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- +capability+ is a capability to add to the previous file
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If you want to add the capability cap_sys_admin to the binary foo,
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you will write :
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----
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/usr/bin/foo f 755 root root - - - - -
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|xattr cap_sys_admin+eip
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----
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You can add several capabilities to a file by using several +|xattr+ lines.
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If you want to add the capability cap_sys_admin and cap_net_admin to the
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binary foo, you will write :
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----
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/usr/bin/foo f 755 root root - - - - -
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|xattr cap_sys_admin+eip
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|xattr cap_net_admin+eip
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----
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