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zgenhostid: accept hostid arguments equal to zero.

Browse Source 
A common usage pattern for zgenhostid, including in the ZFS dracut
module, is running it as:

  zgenhostid $(hostid)

However, zgenhostid only accepted hostid arguments greater than 0, which
meant that, when the output of hostid(1) was "00000000", zgenhostid
would error out, even though 0 is a possible return value for the
gethostid(3) function used by hostid(1):

- On current musl libc, gethostid(3) is a stub that always returns 0.
- On glibc, gethostid(3) will return 0 if /etc/hostid exists but is
  smaller than 4 bytes.

In these cases, it makes more sense for zgenhostid to treat a value of 0
as other parts of the zfs codebase do, meaning that a hostid value
couldn't be determined; therefore, it should attempt to generate a
random value to write into /etc/hostid.

The manpage and usage output have been updated to reflect this.

Whitespace has also been fixed in the usage output.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Georgy Yakovlev <gyakovlev@gentoo.org>
Reviewed-by: Andrew J. Hesford <ajh@sideband.org>
Signed-off-by: Érico Rolim <erico.erc@gmail.com>
Closes #11174
Closes #11189
This commit is contained in:
Érico Rolim 2020-11-10 11:22:27 -03:00 committed by Brian Behlendorf
parent 4352edaafb
commit 9c4b6dbb31
2 changed files with 7 additions and 6 deletions
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10
cmd/zgenhostid/zgenhostid.c
View File

@ -47,10 +47,10 @@ usage(void)
" -h\t\t print this usage and exit\n"
" -o <filename>\t write hostid to this file\n\n"
"If hostid file is not present, store a hostid in it.\n"
"The optional value must be an 8-digit hex number between"
"1 and 2^32-1.\n"
"If no value is provided, a random one will"
"be generated.\n"
"The optional value should be an 8-digit hex number between"
" 1 and 2^32-1.\n"
"If the value is 0 or no value is provided, a random one"
" will be generated.\n"
"The value must be unique among your systems.\n");
exit(EXIT_FAILURE);
/* NOTREACHED */
@ -108,7 +108,7 @@ main(int argc, char **argv)
exit(EXIT_FAILURE);
}
if (input_i < 0x1 || input_i > UINT32_MAX) {
if (input_i > UINT32_MAX) {
fprintf(stderr, "%s\n", strerror(ERANGE));
usage();
}

3
man/man8/zgenhostid.8
View File

@ -54,7 +54,8 @@ instead of default
.It Ar hostid
Specifies the value to be placed in
.Pa /etc/hostid .
It must be a number with a value between 1 and 2^32-1.
It should be a number with a value between 1 and 2^32-1.
If it is 0, zgenhostid will generate a random hostid.
This value
.Sy must
be unique among your systems.