questions about possible remote linux backup issues

[olivierDulac]

Hello,

I also need to do a backup between 2 linux boxes [rh 7.0 "customized" little by little], in case one of them fails. They are networked, and I am planning to mount each one's biggest partition on the other one, and then write from the other one a backup [posssibly a single tar file to avoid using too many inodes, or maybe a tar per /directory, or maybe just using cp, or using any script or program you may recommend] on the NFS-mounted big partition.

Those 2 host are hosted remotely, I can only access with telnet/ssh and ftp. I can't afford to reboot and it doesn't work [I wouldn't even be able to read the screen to troubleshoot...] and it cost A LOT to do anything. In case one host fail I will only have the hosting company reinstall redhat 7.0 ( ) and then I will have to be able to restore my backup on top of it...

I have some important questions before attemtpting anything:

- is it possible that some files can't be backed-up with tar or cp [libraries, files being written into, pipe file, etc] ?

- during restore, what happens with some files like libraries [imagine my ISP restore the failed host with a "vanilla" redhat linux on it, I want to copy over my backups in order to have my last backup instead of the vanilla redhat. What happens when for example I overwrite some shared libraries [especially if this library is used by the program doing the backup] ?

I looked a long time on the web and couldn't find even mentions of those possible problems, so I would be tempted to assume these problems aren't really a problem... but I also believe in murphy's rule. Please make some light on this, or point to the appropriate URLs [I even found a howto about backups: it was in fact a disguised promotion for someone's backup script and didn't adress those issues :/ ]

I fear doing some backups [either with tar, cp, or a script or program] only to find out the day i need it that it can't apply in my situation [where I will be doing the restore remotely, so I want to be able to just overwrite data and have it work... I can't really try-and-fix, it needs to be ok at the first try].

And last question: if the shared libraries are the only problem, do you think I can compile the relevant utilities [tar, cp, etc] to use static libraries and then download them first on the freshly-installed host, and then use the script/command/program to restore and be sure that the shared libraries won't be a problem anymore? Is there some tricky programs I also need to recompile [other than tar and cp for example] ?

Thanks a lot for any help in this matter 🙂

 

[bubba]

I just write a script. Lately I have been using "dump". It is nice because you can use "restore" to browse your archive and recover individual files. So I just script a dump of the directories I want to backup (just home dirs). Then I cron that script in root's crontab.

 

[olivierDulac]

Thanks bubba.

I will look more into dump@restore, but I still fear issues when I restore: I can't really afford to boot on a floppy and/or have a spare root partition to boot on, so i will have to recover the files right on top of the existing partitions. I fear this may cause problems if it happens that I have some dynamically-linked programs [for example the commands like "restore" and whatever other commands it may call [tar? cpio?]] goind beserk when I overwrite one of their libraries "on the fly"...

Anyhone knows how to avoid this? or if dynalically linked libraries are at all dependant on their image file? [maybe any used dynamic lib is only loaded into memory once, and then you can change their image file without changing their memory image? In this case there wouldn't be any problems at all, imho. At least with dyn libraries.... maybe some possible problems with some obscure /dev/device ?]