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Hi. |
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I am trying to build an embedded system to be deployed in a SATA flash |
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disk, and most of the file system will be read-only. |
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There will be a tempfs on /temp and a read-write partition for /var (in |
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fact, a unionfs with the static part of /var and that read-write partition) |
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and the rest of the root tree will (has to) be read-only. |
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|
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There is already a development system with everything working as expected |
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on the final system. |
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|
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Adjusting a few files, when I try to simply put it to a squashfs, the |
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system boots with several errors, when trying to write to "/etc" and "/var" |
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(this last one looks obvious, but there are some init process trying to |
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create temporary files on "/etc"). |
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|
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But even so, I got a prompt, this because one of these adjusted files is |
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"/etc/inittab", where I set up "agetty" to auto-login a user. The system |
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claims that it does not know who is this user (permissions problem, |
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probably). |
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|
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Now, looking on that new issue regarding "/usr" and "/" being on a |
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different partitions, I have found the file in "/etc/initramfs.mounts" , |
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that claims to automagicaly mount specified fstab entries before initramfs |
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gives way to real-root environment. |
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|
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So in this system, for now, there is the directory structure bellow: |
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|
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/.var.rw - here a r/w ext4 partition is to be mounted; |
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/.var.ro - here there are all files and directories expected to be on a |
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usual /var; |
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/var - here a unionfs mount is to join the ones above |
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|
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The part from fstab for this is ("/.var.ro" is present on the squashfs root |
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file system): |
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|
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/dev/sda2 / squashfs |
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noatime,ro 0 1 |
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/dev/sda3 /.var.rw ext4 |
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noatime,defaults 0 2 |
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none /var unionfs |
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nonempty,cow,umask=022,dirs=/.var.rw/=rw:/.var.ro/=ro 0 0 |
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|
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I said it is not yet fully functional because it seems there is something |
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wrong with permissions, because it ends up with a unknown user prompt from |
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which I could list the root directories (something similar is being made to |
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"/etc", so the same results): |
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|
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total 9,0K |
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drwxr-xr-x 23 root root 385 Out 18 14:18 ./ |
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drwxr-xr-x 4 root root 4,0K Set 24 09:46 ../ |
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drwxr-xr-x 47 root root 2,6K Out 17 16:03 .etc.ro/ |
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drwxr-xr-x 2 root root 40 Out 18 15:09 .etc.rw/ |
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drwxr-xr-x 11 root root 262 Out 17 16:03 .var.ro/ |
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drwxr-xr-x 6 root root 4,0K Out 18 14:33 .var.rw/ |
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drwxr-xr-x 2 root root 1,4K Out 7 14:46 bin/ |
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drwxr-xr-x 4 root root 1,0K Out 18 14:15 boot/ |
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d????????? 3 root root 2,3K Ago 1 00:17 dev/ |
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drwxr-xr-x 1 root root 2,6K Out 17 16:03 etc/ |
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drwxr-xr-x 3 root root 54 Ago 22 07:55 home/ |
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lrwxrwxrwx 1 root root 5 Out 7 14:05 lib -> lib64/ |
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drwxr-xr-x 12 root root 3,2K Out 17 08:51 lib64/ |
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drwxr-xr-x 2 root root 28 Ago 1 00:16 media/ |
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drwxr-xr-x 2 root root 28 Ago 1 00:16 opt/ |
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drwxr-xr-x 2 root root 3 Jul 31 22:22 proc/ |
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drwxr-xr-x 2 root root 136 Out 18 14:18 root/ |
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drwxr-xr-x 5 root root 120 Ago 30 08:59 run/ |
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drwxr-xr-x 2 root root 2,9K Out 17 08:51 sbin/ |
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drwxr-xr-x 2 root root 28 Ago 1 00:16 sys/ |
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drwxrwxrwt 2 root root 3 Out 18 14:18 tmp/ |
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drwxr-xr-x 13 root root 267 Out 17 11:18 usr/ |
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d????????? 1 root root 262 Out 17 16:03 var/ |
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Any hints? |
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|
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Thanks |
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Francisco |
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