We need to migrate our GitHub Enterprise from one data center located in Beijing to one in Shanghai. The whole process is not complex but time consuming, it takes us more than one week to finish the migration. I will share some pieces of practice for you.
The current version of GitHub Enterprise running version is 11.10.331, a little bit out of date. it's running on a VirtualBox with 4 CPU cores, 16G memory, the total code takes about 100GByte disk space. According to GitHub staff says, VirtualBox has some performance issues and sometimes even data corruption, so since version 2.0, GitHub no longer support VirtuBox, and they recommend VMware's free vSphere hypervisor, AWS or OpenStack KVM as a replacement.
Considering our new environment in Shanghai, it has quite strict restrictions of choosing platforms from the aspect of security, it's impossible to install something that hasn't been comprehensively investigated and tested, VMware or KVM just out. Since AWS is not so widely spreaded in China and most importantly, it's not possible to host it in a private network, also out. The only choice for us is stilling using VirtualBox.
Now, we need to export the code data from VirtualBox, it has at least two ways, the most straightforward way is to copy the vmdk file, or using VirtualBox's export feature, which you can put the mirror into another OS environment. We choose the first one, copy the vmdk file directly, remember to shutdown the VirtualBox before doing this, or your data will be corrupted.
Originally, We plan to rsync the 100G data from Beijing data center to Shanghai directly via wlan, although both ends are private networks, we can open a DNAT connection from Beijing temporally, so the server hosted in Shanghai can send a active connection to Beijng and begin to transfer, this seems good except that the outbound bandwidth is only 20Mbps, that means, in theory, the tranfer time is 100G*8*1024/20 = 40960s, almost half a day. Actually, there's another issue we can't control, as the data is transfered through the a long distance on the public network, the stability is not guaranteed, what if the connection lost due to some unknown issue? the previous time is in vain.
So, we use a quite traditional way to get it done, take a USB HDD to the data center and copy the data to the HDD, the whole process takes about 2 hours. Later, we rsync the data from HDD to our data center in Shanghai through a leased line.
Now, the raw data is ready for Shanghai, next step it to setup a new VirtualBox instance, it's quite easy, here, we recommend you to install a VNC or something others like ssh X11 forwarding, so you can use a GUI to do the left operations. If you're quite familiar with VBoxManage, that's also ok. The only thing you need to do is to create a new instance, mount the vmdk file as the storage disk.
After booting up the GitHub Enterprise, we found that we can't enter into the http://example.com/setup even we uploaded the license, after opening a ticket, GitHub engineer confirmed that there exists a bug in this version which occasionnlly prevent from entering the management console. In order to continue, we first needed to ssh into the GitHub using admin user, after that, we should remove the previous license file via sudo rm /data/enterprise/enterprise.ghl, then run god restart enterprise-manage. But we were stuck in the fisrt step because we had no sudo permission.
Known the issue, we now require to root the instance. To gain root access we need to boot into recovery mode, just shutdown the VM and power it back on. inside the hypervisor console, hold left shift down while it boots, this will take us to the GRUB menu where we can choose to boot into recovery mode. As the boot process goes so fast, we think up a way to delay the booting by execute the below command outside VirtualBox:
$ VBoxManage modifyvm YOUR_VM_INSTANCE_NAME –bioslogodisplaytime 10000
After that, we can have enough time to press down the button. Note, it's *shift* key, not tab key for VirtualBox. We made a mistake by pressing down the tab unconsciously until we found that stupid accident.
When entering the recovery mode, do as this documentation says. Change the root passwd, and add ssh public key to root/.ssh/authorized_keys. After the server has rebooted normally, we can now use the PubkeyAuthentication method to log in as root.
If everything goes well, we can now upload the license, enter into the management console.
Why we want to enter into the management console? Besides the normal user add/delete management, we also need to change the current authentication process from the built in auth to LDAP-backend auth. The setup is straightforward, we only need to fill out the form with some section values like Host, Port, User ID field, etc. our IT support team provide us. When we click the "Save settings" button, waiting about 10 minutes for it took effect, something weird happened, we can't login with our LDAP account, everytime we try to login, it returned a 500 error. After some troubleshooting, we found that the LDAP setting didn't work because the configuration run wasn't properly triggered when the setting were saved, so the default authentication was still active which we can see from the login welcome portal, it should be something like "Sign in via LDAP", but the fact we saw was "Sign in". Later, we ran enterprise-configure command as our technical support suggested, this time, it worked. Why? We can only suspect that, there were some customizations made to the VirtulBox that caused the configuration process to fail.
After Signing into the new LDAP-backend portal, say, before that it's username is barackobama, the new account name is barackobama.bo. with the new account, we saw a empty page, that make sense, since it's a new account, barackobama.bo which doesn't have any connection with the old account barackobama. If so, all of our code are lost, or we need to git clone with the old account then git push with the new account manually to make the code alive. This can't beat GitHub, just rename the user to the new username with the http://example.com/stafftools/[username]/admin URL. Note that the dot "." will be changed to a hyphen, so remember to rename the user to "barackobama-bo".
Our GitHub Enterprise comes back to life again within a pre-scheduled downtime.