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Re: [Bug-tar] tar1.22 complains when backing up a read-only filesystem
From: |
Andreas Dilger |
Subject: |
Re: [Bug-tar] tar1.22 complains when backing up a read-only filesystem |
Date: |
Wed, 09 Dec 2009 13:35:49 -0700 |
On 2009-12-09, at 06:55, Hill, Shannon wrote:
using tar1.22 built on Centos 5.4 x86_64
sim8/root@/tmp# /usr/local/bin/tar --version
tar (GNU tar) 1.22
...with these options:
time /usr/local/bin/tar \
--create \
--format=pax \
--blocking-factor 2048 \
--totals \
--multi-volume \
--ignore-failed-read \
--exclude .snapshot \
--new-volume-script /root/bin/eot \
--file ${TAPE} .
yields this output (for every file), when . resides on a read-only
file system:
/usr/local/bin/tar: ./tcaputo/views/eclipse/.metadata/.plugins/
org.eclipse.core.resources/.root/.indexes/properties.index: Cannot
utime: Read-only file system
Ironically, it doesn't need to do utime (to set the atime backward)
when the filesystem is mounted read-only. tar should probably check a
"skip_utime" boolean (default = 0) before calling utime(), and if
utime() fails with EROFS that flag is set...
On Linux at least there is also a "O_NOATIME" flag that prevents the
atime from being changed in the first place, just to avoid the need to
write (twice!) to the filesystem for every file touched (once to
update atime, once to revert it). It appears that tar 1.22 has
support for O_NOATIME, but it isn't being used for some reason.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.