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Re: [Bug-tar] what is the point of archiving /proc "files" if you can't
From: |
Paul Eggert |
Subject: |
Re: [Bug-tar] what is the point of archiving /proc "files" if you can't extract them later? |
Date: |
Sat, 5 Nov 2016 19:39:26 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
積丹尼 Dan Jacobson wrote:
Well the archive created sure has a lot of their content. od -c will
prove it to you.
No, the archive contains only metadata, not contents. For example:
$ cd /proc/self
$ tar -cf - limits | od -c
0000000 l i m i t s \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
0000020 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
*
0000140 \0 \0 \0 \0 0 0 0 0 4 4 4 \0 0 0 0 1
0000160 7 5 0 \0 0 0 0 1 7 5 0 \0 0 0 0 0
0000200 0 0 0 0 0 0 0 \0 1 3 0 0 7 5 1 3
0000220 3 1 2 \0 0 1 1 5 7 5 \0 0 \0 \0 \0
0000240 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
*
0000400 \0 u s t a r \0 e g g e r t \0
0000420 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
0000440 \0 \0 \0 \0 \0 \0 \0 \0 \0 e g g e r t \0
0000460 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
*
0024000
This contains metadata, which are something like this:
$ stat limits
File: 'limits'
Size: 0 Blocks: 0 IO Block: 1024 regular empty file
Device: 4h/4d Inode: 304543 Links: 1
Access: (0444/-r--r--r--) Uid: ( 1000/ eggert) Gid: ( 1000/ eggert)
Access: 2016-11-05 19:34:50.841898208 -0700
Modify: 2016-11-05 19:34:50.841898208 -0700
Change: 2016-11-05 19:34:50.841898208 -0700
Birth: -
It does not contain the contents, which are something like this:
$ cat limits
Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes
Max stack size 8720000 unlimited bytes
Max core file size 0 unlimited bytes
Max resident set unlimited unlimited bytes
Max processes 59772 59772 processes
Max open files 1024 65536 files
Max locked memory 65536 65536 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 59772 59772 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0
Max realtime timeout unlimited unlimited us