Bash – Need to press enter to get prompt after executing udev script

bashcommand linescripting

I have set a simple udev rule for my Raspberry Pi (Debian) to automatically mount an USB HDD. It just runs a script which mounts all devices in /etc/fstab since it's the only one I have and I'm going to have there.
I just need that but I saw that there were some environment variables that got passed to the script and tried to get it to print the label of the drive and the device node name for example just to experiment a bit.

I got it to work, but now when I plug it I get for example:

pi@Gawain ~ $ Disk TOSHIBA_EXT (/dev/sda1) plugged in.Mounting...

And then in the next line I get no prompt, but it's not that the script hasn't exited correctly or anything, it's waiting for input and if I type anything like "pwd" for example it works, it's just that it shows no prompt.

I'm really not concerned about this since it's just a minor cosmetic thing, and I'll probably leave the script to just mount the drive silently, but I feel curious about why it's behaving that way.

udev rule:
KERNEL=="sd*1", ACTION=="add", RUN+="/home/pi/scripts/mountUSB.sh"

mountUSB.sh:

#!/bin/bash
CONSOLE="/dev/$(who | awk '{print $2}')"
echo "Disk $ID_FS_LABEL ($DEVNAME) plugged in.Mounting..." > $CONSOLE
sudo mount -a

Best Answer

When you are printing straight to the terminal, your shell doesn't know about it, so it doesn't know to print its prompt again. You would get similar behavior running e.g. (sleep 1; echo foo) &.

I would suggest either not printing from your udev rule (that seems like the more usual thing to do: be quiet unless something wrong happened), or living with it, knowing that nothing is really broken here; the messages pushed straight to your terminal are parasitic as far as you shell is concerned.

First: Increase the disk size.

In ESXi this is simple, just increase the size of the virtual disk. Now you have a bigger hard drive but you still need to a) increase the partition size and b) resize the filesystem.

Second: Increase the partition size.

You can use fdisk to change the partition table while running. The stock Ubuntu install has created 3 partitions: one primary (sda1), one extended (sda2) with a single logical partition (sda5) in it. The extended partition is simply used for swap, so I could easily move it without losing any data.

Delete the primary partition
Delete the extended partition
Create a new primary partition starting at the same sector as the original one just with a bigger size (leave some for swap)
Create a new extended partition with a logical partition in it to hold the swap space

    me@ubuntu:~$ sudo fdisk /dev/sda
     
    Command (m for help): p
     
    Disk /dev/sda: 268.4 GB, 268435456000 bytes
    255 heads, 63 sectors/track, 32635 cylinders, total 524288000 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x000e49fa
     
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1   *        2048   192940031    96468992   83  Linux
    /dev/sda2       192942078   209713151     8385537    5  Extended
    /dev/sda5       192942080   209713151     8385536   82  Linux swap / Solaris
     
    Command (m for help): d
    Partition number (1-5): 1
     
    Command (m for help): d
    Partition number (1-5): 2
     
    Command (m for help): n
    Partition type:
       p   primary (0 primary, 0 extended, 4 free)
       e   extended
    Select (default p): p
    Partition number (1-4, default 1):
    Using default value 1
    First sector (2048-524287999, default 2048):
    Using default value 2048
    Last sector, +sectors or +size{K,M,G} (2048-524287999, default 524287999): 507516925
     
    Command (m for help): p
     
    Disk /dev/sda: 268.4 GB, 268435456000 bytes
    255 heads, 63 sectors/track, 32635 cylinders, total 524288000 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x000e49fa
     
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1            2048   507516925   253757439   83  Linux
     
    Command (m for help): n
    Partition type:
       p   primary (1 primary, 0 extended, 3 free)
       e   extended
    Select (default p): e
    Partition number (1-4, default 2): 2
    First sector (507516926-524287999, default 507516926):
    Using default value 507516926
    Last sector, +sectors or +size{K,M,G} (507516926-524287999, default 524287999):
    Using default value 524287999
     
    Command (m for help): p
     
    Disk /dev/sda: 268.4 GB, 268435456000 bytes
    255 heads, 63 sectors/track, 32635 cylinders, total 524288000 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x000e49fa
     
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1            2048   507516925   253757439   83  Linux
    /dev/sda2       507516926   524287999     8385537    5  Extended
     
    Command (m for help): n
    Partition type:
       p   primary (1 primary, 1 extended, 2 free)
       l   logical (numbered from 5)
    Select (default p): l
    Adding logical partition 5
    First sector (507518974-524287999, default 507518974):
    Using default value 507518974
    Last sector, +sectors or +size{K,M,G} (507518974-524287999, default 524287999):
    Using default value 524287999
     
    Command (m for help): p
     
    Disk /dev/sda: 268.4 GB, 268435456000 bytes
    255 heads, 63 sectors/track, 32635 cylinders, total 524288000 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x000e49fa
     
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1            2048   507516925   253757439   83  Linux
    /dev/sda2       507516926   524287999     8385537    5  Extended
    /dev/sda5       507518974   524287999     8384513   83  Linux
     
    Command (m for help): t
    Partition number (1-5): 5
     
    Hex code (type L to list codes): 82
    Changed system type of partition 5 to 82 (Linux swap / Solaris)
     
    Command (m for help): p
     
    Disk /dev/sda: 268.4 GB, 268435456000 bytes
    255 heads, 63 sectors/track, 32635 cylinders, total 524288000 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x000e49fa
     
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1            2048   507516925   253757439   83  Linux
    /dev/sda2       507516926   524287999     8385537    5  Extended
    /dev/sda5       507518974   524287999     8384513   82  Linux swap / Solaris
     
    Command (m for help): w
    The partition table has been altered!
     
    Calling ioctl() to re-read partition table.
     
    WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
    The kernel still uses the old table. The new table will be used at
    the next reboot or after you run partprobe(8) or kpartx(8)
    Syncing disks.
     
    me@ubuntu:~$ sudo reboot

I noticed afterwards that I didn’t set the bootable flag but apparently you don’t really need it.

Third: Enlargen the filesystem.

You can do this with resize2fs online on a mounted partition.

me@ubuntu:~$ df -h
Filesystem      Size  Used Avail Use% Mounted
on /dev/sda1        91G   86G   12M 100% / udev            3.9G  4.0K 
3.9G   1% /dev tmpfs           1.6G  696K  1.6G   1% /run none            5.0M     0  5.0M   0% /run/lock none            3.9G  144K  3.9G   1% /run/shm none            100M   16K  100M   1% /run/user  
me@ubuntu:~$ sudo resize2fs /dev/sda1
resize2fs 1.42.5 (29-Jul-2012)
Filesystem at /dev/sda1 is mounted on /; on-line resizing required
old_desc_blocks = 6, new_desc_blocks = 16 The filesystem on /dev/sda1
is now 63439359 blocks long.
me@ubuntu:~$ df -h
Filesystem      Size
Used Avail Use% Mounted on /dev/sda1       239G   86G  142G  38% /
udev            3.9G   12K  3.9G   1% /dev tmpfs           1.6G  696K 
1.6G   1% /run none            5.0M     0  5.0M   0% /run/lock none            3.9G  152K  3.9G   1% /run/shm none            100M   36K  100M   1% /run/user

Slight catch: After rebooting the swap space wasn’t active. Turned out you need to run mkswap, adjust /etc/fstab to the new UUID and turn the swap on

me@ubuntu:~$ sudo mkswap /dev/sda5 
Setting up swapspace version 1, size = 8384508 KiB no label, UUID=141d401a-b49d-4a96-9b85-c130cb0de40a

Edit /etc/fstab to replace the UUID for the old swap partition with the new one from mkswap, then turn on swap

me@ubuntu:~$ sudo swapon --all --verbose 
swapon: /dev/sda5: found swap signature: version 1, page-size 4, same byte order
swapon: /dev/sda5: pagesize=4096, swapsize=8585740288, devsize=8585741312

Best Answer

Related Solutions

Bash Command – Printing and Saving the Last Bash Input Command

Command Line – How to Resize an ext4 Partition

First: Increase the disk size.

Second: Increase the partition size.

Third: Enlargen the filesystem.

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