The bootable flag on partition 1 is enabled now.

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
Disk <removed>: 50 MiB, 52428800 bytes, 102400 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / <removed> bytes
Disklabel type: dos
Disk identifier: <removed>

Device     Boot Start    End Sectors Size Id Type
<removed>1  *     2048   8191    6144   3M 83 Linux
<removed>2        8192  14335    6144   3M 82 Linux swap / Solaris
<removed>3       14336  20479    6144   3M 83 Linux
<removed>4       20480 102399   81920  40M  5 Extended
<removed>5       22528  28671    6144   3M 83 Linux
<removed>6       30720 102399   71680  35M 83 Linux