我最近安装了 Debian Stable 12.7（使用从官方网站下载的 iso 文件创建的安装 DVD）。除此之外，它运行良好。我将其安装在逻辑分区中。然而，在安装过程中，grub 并未添加硬盘第一个分区上的 Windows7。该分区仍在那里，我可以访问该分区上的所有文件。
可能存在什么问题以及如何解决？
我最近安装了 Debian Stable 12.7，它运行良好。我尝试连接外部硬盘（我假设它将具有 NTFS 分区）。硬盘上的灯亮了，它开始发出嗡嗡声，但没有连接。以下是“dmesg”命令的输出：
[ 299.027072] ISO 9660 Extensions: Microsoft Joliet Level 1
[ 299.030692] ISOFS: changing to secondary root
[ 461.519421] usb 1-1.3.3: USB disconnect, device number 5
[ 461.780067] usb 1-1.3.3: new high-speed USB device number 6 using ehci-pci
[ 461.888648] usb 1-1.3.3: New USB device found, idVendor=1a40, idProduct=0101, bcdDevice= 1.00
[ 461.888656] usb 1-1.3.3: New USB device strings: Mfr=0, Product=1, SerialNumber=0
[ 461.888660] usb 1-1.3.3: Product: USB2.0 HUB
[ 461.889073] hub 1-1.3.3:1.0: USB hub found
[ 461.889248] hub 1-1.3.3:1.0: 4 ports detected
[ 462.612070] usb 1-1.3.3.3: new high-speed USB device number 7 using ehci-pci
[ 462.821973] usb 1-1.3.3.3: New USB device found, idVendor=1058, idProduct=2626, bcdDevice=10.34
[ 462.821981] usb 1-1.3.3.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 462.821985] usb 1-1.3.3.3: Product: My Passport 2626
[ 462.821987] usb 1-1.3.3.3: Manufacturer: Western Digital
[ 462.821989] usb 1-1.3.3.3: SerialNumber: 575832324139335238333439
[ 462.871255] usb-storage 1-1.3.3.3:1.0: USB Mass Storage device detected
[ 462.871439] scsi host6: usb-storage 1-1.3.3.3:1.0
[ 462.871558] usbcore: registered new interface driver usb-storage
[ 462.878172] usbcore: registered new interface driver uas
[ 463.889586] scsi 6:0:0:0: Direct-Access WD My Passport 2626 1034 PQ: 0 ANSI: 6
[ 463.890390] scsi 6:0:0:1: Enclosure WD SES Device 1034 PQ: 0 ANSI: 6
[ 463.900858] sd 6:0:0:0: Attached scsi generic sg3 type 0
[ 463.901059] scsi 6:0:0:1: Attached scsi generic sg4 type 13
[ 463.904605] sd 6:0:0:0: [sdc] Spinning up disk...
[ 464.912081] ..................................................................................................not responding...
[ 576.243597] sd 6:0:0:0: [sdc] Read Capacity(10) failed: Result: hostbyte=DID_OK driverbyte=DRIVER_OK
[ 576.243607] sd 6:0:0:0: [sdc] Sense Key : Not Ready [current]
[ 576.243610] sd 6:0:0:0: [sdc] Add. Sense: Logical unit is in process of becoming ready
[ 578.244590] sd 6:0:0:0: [sdc] 0 512-byte logical blocks: (0 B/0 B)
[ 578.244599] sd 6:0:0:0: [sdc] 0-byte physical blocks
[ 580.245617] sd 6:0:0:0: [sdc] Test WP failed, assume Write Enabled
[ 582.246626] sd 6:0:0:0: [sdc] Asking for cache data failed
[ 582.246639] sd 6:0:0:0: [sdc] Assuming drive cache: write through
[ 582.247059] sd 6:0:0:0: [sdc] Attached SCSI disk
[ 596.259393] scsi 6:0:0:1: Failed to get diagnostic page 0x1
[ 596.259405] scsi 6:0:0:1: Failed to bind enclosure -19
[ 596.259435] ses 6:0:0:1: Attached Enclosure device
问题是什么？如何解决？
我有一个 Linux 发行版，它在 MBR 上安装了 grub。
然后我在另一个分区上安装了第二个 Linux 发行版，但没有在其中安装 grub。
然后我去了第一个 Linux 发行版并运行了 update-grub。所以第二个 Linux 发行版也被选中，并在启动时出现在菜单中。
现在我想删除第一个 Linux 发行版。如何在第二个 Linux 发行版中安装 grub，以便它也链接到 MBR 中的 grub？
我正在尝试按照此页面上的说明在 Debian Stable (Buster) 上安装最新的 R 包：https ://cloud.r-project.org/
我在 /etc/apt/sources.list 中添加了以下内容：
deb https://cran.csiro.au/bin/linux/debian buster-cran35/
但是，当我运行时sudo apt-get update，出现以下错误：
$ sudo apt-get update
Hit:1 http://deb.debian.org/debian buster InRelease
Hit:2 http://deb.debian.org/debian-security buster/updates InRelease
Hit:3 http://deb.debian.org/debian buster-updates InRelease
Hit:4 http://deb.debian.org/debian buster-backports InRelease
Get:5 https://cran.csiro.au/bin/linux/debian buster-cran35/ InRelease [4,375 B]
Err:5 https://cran.csiro.au/bin/linux/debian buster-cran35/ InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FCAE2A0E115C3D8A
Reading package lists... Done
W: GPG error: https://cran.csiro.au/bin/linux/debian buster-cran35/ InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FCAE2A0E115C3D8A
E: The repository 'https://cran.csiro.au/bin/linux/debian buster-cran35/ InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
尽管进行了以下尝试，但我无法摆脱此 GPG 错误：
sudo apt-get install debian-keyring
sudo launchpad-getkeys
sudo aptitude install debian-archive-keyring
我该如何解决这个错误？