OpenWRT and Bare Metal BackUps: Difference between revisions

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===Backing Up===

The "Backing Up" or BackUp Process is the first part of ~~the~~ cloning a system too. In syntax examples, devices are assumed to be in /dev.

The "Backing Up" or BackUp Process is the first part of cloning a system too. So why not just use something like an external drive bay to clone the disk / SSD to another drive? Because that involves removing the drive. The end objective is to be able to do a live, bare metal cloning process.

==== Assumptions ====

In syntax examples, devices are assumed to be in /dev.

====Relevant "Partitions" of an OpenWRT x86====

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...and finally, issue this command, just to make sure everything is flushed from cache / memory: <code>sync</code>

====Syntax Notes for DD====

===Syntax Notes for DD===

*if: Input File (or Device)

*of: Output File (or Device)

*bs: "~~How much~~ to copy from ~~one device~~ to ~~another at a time"~~

*bs: "Chunk" size to copy from it= to of=

*conv=noerror: "Don't stop, just do what I told you to do, and don't give an excuse"

*progress = status: Show the progress of the copy process (only for a certain version of DD and up)

*conv=sync: Write all buffered blocks to disk (just to be safe, but can cause 'out of space' issues with MBR and "MBR Gap")

*skip: Skips X number of sectors for the ''input ( if= )''

*seek: Skips X number of sectors for the ''output ( of= )''

...and finally, DD seems to be a Zero Based utility, similar to how Disks (and other items like Intel SATA Ports, etc.) are numbered starting from Zero ( 0 ). So setting skip=511 will skip sectors 0 through 511, for a total of 512 sectors.

=== Overlay, OverlayFS, Union Mount, SquashFS, F2FS, and more... ===

Real quick, here's what's going on with a typical Router based installation of OpenWRT that is stored on Flash Memory Storage.

OpenWRT is essentially installed on devices as if all of it's code were stored in an EPROM and just plugged into the board of a router. There are a bunch of abstraction layers that make this possible, both in the installation and function of OpenWRT, but that's what is happening.

How is it done? Using the Overlay / Union Mount capabilities of Linux. Sorry, not here to explain that fully, hence the above links.

=== Backing up the /overlay Directory ===

Ideally (since LVM isn't typically available to do "Volume Shadow Copies"), one would boot to an alternative OS, use DD to clone the /overlay "Partition" / "Device". Easy with an x86_64 based install of OpenWRT, but also very possible with a Router based on Flash Memory Storage too. For the Router scenario, again ideally, if the /overlay "Partition" / "Device" is on an external USB Flash Drive (as it should be if a router has a USB 3.0 port), just pop it into a "Linux Box" (virtual or otherwise) for backing up. It can also be done "live" without much chance of something being modified during the cloning process.

* Make a BackUp: While booted to an alternate OS (Rocky Linux, another OpenWRT install on a USB Flash Drive, etc.), in this example, booted to another OS, do... Wait, but first;

** Locate where the /overlay Partition is;

*** LSBLK will show the connection between the /overlay Directory and what it is "connected to" (hint for x86 systems, look in the /boot/grub/grub.cfg file)

**** For an OpenWRT install with /overlay on a USB Flash Drive: /overlay will be on /dev/sdXy (where X is a letter and y is a number, example: sda1)

**** For an OpenWRT install with /overlay on a SATA Disk Drive / SSD: /overlay will be on a Loop Device, roughly equivalent to a VHD or VHDX File where a file represents a storage device

***** Use this command: losetup -a (it will display something like this: /dev/loop0: (Some Numbers) (/sda2), offset 3014656 (/dev/loop0 is the device and /sda2 is the "file", actually a real drive))

** "Create" a LOOP Device (For an x86 (used interchangeably with x86_64, yes, yes, don't say it));

*** Generic Syntax: losetup -o OffsetInBytes /dev/loopX /WhatEverPath/WhatEverFileName

*** OpenWRT specific Syntax: losetup -o 3014656 -fP /WhatEverPath/WhatEverFileName (3014656* is the offset picked by the OpenWRT developers, losetup will pick the next available LOOP#)

*** OpenWRT Syntax Example: losetup -o 3014656 -fP /mnt/sda1/OpenWRT_BackUp.img

** Mount the LOOP Device (again for an x86 system)

*** Example: mount -t f2fs /dev/loop1 /mnt/loop1 (mkdir /mnt/loop1 before this command of course)

** ...and that's it for x86 devices. From there, just cp

<nowiki>*</nowiki>If you haven't spotted it yet, but you've been asking, "Where is that file that OpenWRT mounts a Directory named /overlay as a LOOP Device?" Answer: There is no file. It is simply a sector on the Disk / SSD Drive to the end of it. And you might ask, "But won't it be overwritten?" Answer: Nope, because everything before it is considered ROM (as in no write), so it won't expand. And yes that means the entire disk drive (well, at least the OpenWRT partitions) is considered a File that breaks down into a ROM Section and an /overlay Section.

Why 3014656 Bytes as the offset? Well, it works out to 5888 Sectors (512 Bytes / Sector, $1700 (that's Commodore Hexadecimal Notation)), 1472 Sectors (if translated to 2048 Bytes / Sector, $5CO), so nothing really jumps out. If it was the 1980s, there might be some unique point in the CHS format where this makes sense. Some other alignment? Doesn't make any sense with SSDs, but maybe something with HDDs. PI ( π )? Nope, that's 3.141592. Maximum "ROM" size (with room left for expansion)? That seems so much like Bill Gate's comment on 640K should probably be about enough for anyone, when putting important stuff above the top of RAM, thus blocking easy expansion and requiring workarounds.

mount -t f2fs /dev/loop1 /mnt/loop1

=== More on the LOSETUP Command ===

==== Create a "Device" to Mount, IE Associate a File with a Loop Device Node[edit | edit source] ====

losetup -fP WhatEverImageName.img (To see mounted "Devices": losetup -a), (f = File Name to configure as a Loop Device, P = Scan Partition Size, a = Show All Loop Devices, b = sector size)

"Man" Page for LOSETUP: <nowiki>https://man7.org/linux/man-pages/man8/losetup.8.html</nowiki>

Loop Device: <nowiki>https://en.wikipedia.org/wiki/Loop_device</nowiki>

==== Mount the Image[edit | edit source] ====

mount -t squashfs /dev/loop7 /mnt/squash

====~~Questions About Stuff~~====

Keep in mind this only works with IMG Files created from Partitions. If an entire disk drive is imaged, the above method won't work. However...

==== Mount an Image of an Entire Disk[edit | edit source] ====

If an entire disk is imaged with DD, then a "map" of it can be viewed with CFDISK: cfdisk /dev/WhatEverLoopDevice (Example: cfdisk /dev/loop5) (Remember, use losetup -a to see "Devices")

Examining the output of CFDISK will show the names of the individual Partitions available: /dev/WhatEverLoopDevicePx (Example: /dev/loop6p1).

With the above information garnered from CFDISK, then mount individual Partitions: mount -t WhatEverFileSystem (squashfs, ext4, ntfs-3g, etc.) /dev/WhatEverLoopDevice /mnt/WhatEverMountPoint: mount -t squashfs /dev/loop6p2 /mnt/Loop6/p2 (Also: losetup -d /dev/WhatEverLoopDevice will delete the loop device)

==== Note on: LOSETUP -d WhatEverLoopDeviceName[edit | edit source] ====

Bad news. The delete command doesn't always work. After issuing the command on a legitimate Loop Device, and with no errors, the Loop Device will persist. Checking it with LOSETUP -a shows it is still there. Accessing it with CFDISK or MOUNT still works. Oh, well. Windows solution time. Reboot.

<br />

===FAQs===

*Why 511 sectors?

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Line 133:

====GRUB====

OpenWRT specifically mentions GRUB 2 in their documentation. But the way it works on an x86_64 EXT4 installation of OpenWRT would convince anyone that it is Legacy GRUB (except for the GNU GRUB version 2.02 heading at the top of the screen). The way it is configured via /etc/grub/grub.cfg would also convince anyone that Legacy GRUB was being used. So, the conclusion is that GRUB 2.02 is indeed being used, but since it is backwards compatible, it is in 'Legacy Mode'.

=== Rant on Backing Up OpenWRT (Not just the configuration files, but an entire 'Drive' (Flash, SSD, etc.))[edit | edit source] ===

How can the entire OpenWRT installation be backed up in a fashion similar to Acronis products, Clonezilla, etc.?

The first answer is that there is no built in facility to do that. Dang! Why not? Well, first of all, OpenWRT is intended to be installed on small router devices where this type of backup (Disk / Drive Imaging, Bare Metal BackUp, etc.) just isn't a thing. Second, and largely because of something mentioned in the first item, is that a program like that can't be crammed into a small enough space to fit on small router device.

==== Spoiler Alert: RESTIC[edit | edit source] ====

What about Baquacil, err, wait, that's a pool chemical. Bactine! No, that's the antiseptic. RESTIC! Yup, that's the utility for backing up in OpenWRT (the only one)

Sadly it's like EDLIN VS Microsoft Word. No offense to the nice RETIC people. It does it's job and works reliably. But seems as if was made in the 1980s (it was actually done in the 20 teens). Again, no offense, it has a ton of features and seems bullet proof.

And most of all, RESTIC is for backing up files on a Disk, Volume, or Partition. It is not capable of (nor is it intended for) backing up an entire disk or partition, including boot sectors, file tables, etc. It is not a Disk / SSD or Partition Imaging device.

Wah! But what if I want to do it anyway because... Well, because I want to

==== Other Choices[edit | edit source] ====

Clonezilla? Yup, great, but one issue. One has to boot from the Clonezilla CD / DVD / USB Flash Drive / ISO to do it. Router off, Clonezilla on.

Again; WAH! I want to do it with the Router still fully functional, IE from within OpenWRT.

==== What About DD?[edit | edit source] ====

Perfect! Except for one thing: Files might change right in the middle of a backup (because it takes a long time). Remember DD has no capability or concept of "Volume Shadow Copy" (Note: RESTIC doesn't have the capability, but it does have the concept of it, however that would require converting the entire OpenWRT install over to an LVM based Disk / SSD / Whatever 'Layout'.)

==== Ideal Objective[edit | edit source] ====

Ideally, the only solution would seem to be something like Acronis for Linux (or some other commercial product). Or something like RUBackUp and / or FSArchiver. The latter requiring the above noted conversion of OpenWRT over to an LVM based Disk / SSD / FlashDrive system. That's a lot of work. The best option would be making DD aware of Volume Snapshots and doing it that way. Ongoing work with this experiment will be to attempt changing the disk layout to include an LVM volume that allows for "Volume Shadow Copy" (Volume Snapshot, etc., IE, the Linux equivalent of that Windows feature) and using DD for a Bare Metal BackUp!

==== Cop Out, err, Respect![edit | edit source] ====

Please remember, none of this is rant is intended to be disrespectful to the OpenWRT, RESTIC, or anyone else that might have felt slighted. It is simply a colorful way of noting how in the software world, once someone is given something, the inevitable question and desire of 'What else can it do?" comes up. That's what this is about

@@ Line 4: / Line 4: @@
 ===Backing Up===
-The "Backing Up" or BackUp Process is the first part of the cloning a system too.  In syntax examples, devices are assumed to be in /dev.
+The "Backing Up" or BackUp Process is the first part of cloning a system too.  So why not just use something like an external drive bay to clone the disk / SSD to another drive?  Because that involves removing the drive.  The end objective is to be able to do a live, bare metal cloning process.
+==== Assumptions ====
+In syntax examples, devices are assumed to be in /dev.
 ====Relevant "Partitions" of an OpenWRT x86====
@@ Line 40: / Line 43: @@
 ...and finally, issue this command, just to make sure everything is flushed from cache / memory: <code>sync</code>
-====Syntax Notes for DD====
+===Syntax Notes for DD===
 *if: Input File (or Device)
 *of: Output File (or Device)
-*bs: "How much to copy from one device to another at a time"
+*bs: "Chunk" size to copy from it= to of=
 *conv=noerror: "Don't stop, just do what I told you to do, and don't give an excuse"
 *progress = status: Show the progress of the copy process (only for a certain version of DD and up)
 *conv=sync: Write all buffered blocks to disk (just to be safe, but can cause 'out of space' issues with MBR and "MBR Gap")
 *skip: Skips X number of sectors for the ''input ( if= )''
 *seek: Skips X number of sectors for the ''output ( of= )''
+...and finally, DD seems to be a Zero Based utility, similar to how Disks (and other items like Intel SATA Ports, etc.) are numbered starting from Zero ( 0 ).  So setting skip=511 will skip sectors 0 through 511, for a total of 512 sectors.
+=== Overlay, OverlayFS, Union Mount, SquashFS, F2FS, and more... ===
+Real quick, here's what's going on with a typical Router based installation of OpenWRT that is stored on Flash Memory Storage.
+OpenWRT is essentially installed on devices as if all of it's code were stored in an EPROM and just plugged into the board of a router. There are a bunch of abstraction layers that make this possible, both in the installation and function of OpenWRT, but that's what is happening.
+How is it done? Using the Overlay / Union Mount capabilities of Linux. Sorry, not here to explain that fully, hence the above links.
+=== Backing up the /overlay Directory ===
+Ideally (since LVM isn't typically available to do "Volume Shadow Copies"), one would boot to an alternative OS, use DD to clone the /overlay "Partition" / "Device". Easy with an x86_64 based install of OpenWRT, but also very possible with a Router based on Flash Memory Storage too. For the Router scenario, again ideally, if the /overlay "Partition" / "Device" is on an external USB Flash Drive (as it should be if a router has a USB 3.0 port), just pop it into a "Linux Box" (virtual or otherwise) for backing up. It can also be done "live" without much chance of something being modified during the cloning process.
+* Make a BackUp: While booted to an alternate OS (Rocky Linux, another OpenWRT install on a USB Flash Drive, etc.), in this example, booted to another OS, do... Wait, but first;
+** Locate where the /overlay Partition is;
+*** LSBLK will show the connection between the /overlay Directory and what it is "connected to" (hint for x86 systems, look in the /boot/grub/grub.cfg file)
+**** For an OpenWRT install with /overlay on a USB Flash Drive: /overlay will be on /dev/sdXy (where X is a letter and y is a number, example: sda1)
+**** For an OpenWRT install with /overlay on a SATA Disk Drive / SSD: /overlay will be on a Loop Device, roughly equivalent to a VHD or VHDX File where a file represents a storage device
+***** Use this command: losetup -a (it will display something like this: /dev/loop0: (Some Numbers) (/sda2), offset 3014656 (/dev/loop0 is the device and /sda2 is the "file", actually a real drive))
+** "Create" a LOOP Device (For an x86 (used interchangeably with x86_64, yes, yes, don't say it));
+*** Generic Syntax: losetup -o OffsetInBytes /dev/loopX /WhatEverPath/WhatEverFileName
+*** OpenWRT specific Syntax: losetup -o 3014656 -fP /WhatEverPath/WhatEverFileName (3014656* is the offset picked by the OpenWRT developers, losetup will pick the next available LOOP#)
+*** OpenWRT Syntax Example: losetup -o 3014656 -fP /mnt/sda1/OpenWRT_BackUp.img
+** Mount the LOOP Device (again for an x86 system)
+*** Example: mount -t f2fs /dev/loop1 /mnt/loop1 (mkdir /mnt/loop1 before this command of course)
+** ...and that's it for x86 devices. From there, just cp
+<nowiki>*</nowiki>If you haven't spotted it yet, but you've been asking, "Where is that file that OpenWRT mounts a Directory named /overlay as a LOOP Device?" Answer: There is no file. It is simply a sector on the Disk / SSD Drive to the end of it. And you might ask, "But won't it be overwritten?" Answer: Nope, because everything before it is considered ROM (as in no write), so it won't expand. And yes that means the entire disk drive (well, at least the OpenWRT partitions) is considered a File that breaks down into a ROM Section and an /overlay Section.
+Why 3014656 Bytes as the offset? Well, it works out to 5888 Sectors (512 Bytes / Sector, $1700 (that's Commodore Hexadecimal Notation)), 1472 Sectors (if translated to 2048 Bytes / Sector, $5CO), so nothing really jumps out. If it was the 1980s, there might be some unique point in the CHS format where this makes sense. Some other alignment? Doesn't make any sense with SSDs, but maybe something with HDDs. PI ( π )? Nope, that's 3.141592. Maximum "ROM" size (with room left for expansion)? That seems so much like Bill Gate's comment on 640K should probably be about enough for anyone, when putting important stuff above the top of RAM, thus blocking easy expansion and requiring workarounds.
+mount -t f2fs /dev/loop1 /mnt/loop1
+=== More on the LOSETUP Command ===
+==== Create a "Device" to Mount, IE Associate a File with a Loop Device Node[edit | edit source] ====
+losetup -fP WhatEverImageName.img (To see mounted "Devices": losetup -a), (f = File Name to configure as a Loop Device, P = Scan Partition Size, a = Show All Loop Devices, b = sector size)
+"Man" Page for LOSETUP: <nowiki>https://man7.org/linux/man-pages/man8/losetup.8.html</nowiki>
+Loop Device: <nowiki>https://en.wikipedia.org/wiki/Loop_device</nowiki>
+==== Mount the Image[edit | edit source] ====
+mount -t squashfs /dev/loop7 /mnt/squash
-====Questions About Stuff====
+Keep in mind this only works with IMG Files created from Partitions. If an entire disk drive is imaged, the above method won't work. However...
+==== Mount an Image of an Entire Disk[edit | edit source] ====
+If an entire disk is imaged with DD, then a "map" of it can be viewed with CFDISK: cfdisk /dev/WhatEverLoopDevice (Example: cfdisk /dev/loop5) (Remember, use losetup -a to see "Devices")
+Examining the output of CFDISK will show the names of the individual Partitions available: /dev/WhatEverLoopDevicePx (Example: /dev/loop6p1).
+With the above information garnered from CFDISK, then mount individual Partitions: mount -t WhatEverFileSystem (squashfs, ext4, ntfs-3g, etc.) /dev/WhatEverLoopDevice /mnt/WhatEverMountPoint: mount -t squashfs /dev/loop6p2 /mnt/Loop6/p2 (Also: losetup -d /dev/WhatEverLoopDevice will delete the loop device)
+==== Note on: LOSETUP -d WhatEverLoopDeviceName[edit | edit source] ====
+Bad news. The delete command doesn't always work. After issuing the command on a legitimate Loop Device, and with no errors, the Loop Device will persist. Checking it with LOSETUP -a shows it is still there. Accessing it with CFDISK or MOUNT still works. Oh, well. Windows solution time. Reboot.
+<br />
+===FAQs===
 *Why 511 sectors?
@@ Line 74: / Line 133: @@
 ====GRUB====
 OpenWRT specifically mentions GRUB 2 in their documentation.  But the way it works on an x86_64 EXT4 installation of OpenWRT would convince anyone that it is Legacy GRUB (except for the GNU GRUB   version 2.02 heading at the top of the screen).  The way it is configured via /etc/grub/grub.cfg would also convince anyone that Legacy GRUB was being used.  So, the conclusion is that GRUB 2.02 is indeed being used, but since it is backwards compatible, it is in 'Legacy Mode'.
+=== Rant on Backing Up OpenWRT (Not just the configuration files, but an entire 'Drive' (Flash, SSD, etc.))[edit | edit source] ===
+How can the entire OpenWRT installation be backed up in a fashion similar to Acronis products, Clonezilla, etc.?
+The first answer is that there is no built in facility to do that. Dang! Why not? Well, first of all, OpenWRT is intended to be installed on small router devices where this type of backup (Disk / Drive Imaging, Bare Metal BackUp, etc.) just isn't a thing. Second, and largely because of something mentioned in the first item, is that a program like that can't be crammed into a small enough space to fit on small router device.
+==== Spoiler Alert: RESTIC[edit | edit source] ====
+What about Baquacil, err, wait, that's a pool chemical. Bactine! No, that's the antiseptic. RESTIC! Yup, that's the utility for backing up in OpenWRT (the only one)
+Sadly it's like EDLIN VS Microsoft Word. No offense to the nice RETIC people. It does it's job and works reliably. But seems as if was made in the 1980s (it was actually done in the 20 teens). Again, no offense, it has a ton of features and seems bullet proof.
+And most of all, RESTIC is for backing up files on a Disk, Volume, or Partition. It is not capable of (nor is it intended for) backing up an entire disk or partition, including boot sectors, file tables, etc. It is not a Disk / SSD or Partition Imaging device.
+Wah! But what if I want to do it anyway because... Well, because I want to
+==== Other Choices[edit | edit source] ====
+Clonezilla? Yup, great, but one issue. One has to boot from the Clonezilla CD / DVD / USB Flash Drive / ISO to do it. Router off, Clonezilla on.
+Again; WAH! I want to do it with the Router still fully functional, IE from within OpenWRT.
+==== What About DD?[edit | edit source] ====
+Perfect! Except for one thing: Files might change right in the middle of a backup (because it takes a long time). Remember DD has no capability or concept of "Volume Shadow Copy" (Note: RESTIC doesn't have the capability, but it does have the concept of it, however that would require converting the entire OpenWRT install over to an LVM based Disk / SSD / Whatever 'Layout'.)
+==== Ideal Objective[edit | edit source] ====
+Ideally, the only solution would seem to be something like Acronis for Linux (or some other commercial product). Or something like RUBackUp and / or FSArchiver. The latter requiring the above noted conversion of OpenWRT over to an LVM based Disk / SSD / FlashDrive system. That's a lot of work. The best option would be making DD aware of Volume Snapshots and doing it that way. Ongoing work with this experiment will be to attempt changing the disk layout to include an LVM volume that allows for "Volume Shadow Copy" (Volume Snapshot, etc., IE, the Linux equivalent of that Windows feature) and using DD for a Bare Metal BackUp!
+==== Cop Out, err, Respect![edit | edit source] ====
+Please remember, none of this is rant is intended to be disrespectful to the OpenWRT, RESTIC, or anyone else that might have felt slighted. It is simply a colorful way of noting how in the software world, once someone is given something, the inevitable question and desire of 'What else can it do?" comes up. That's what this is about