gpg or gpg2 gpg: signing failed: Inappropriate ioctl for device

 If you ever get the following error, while trying to sign with gpg:

gpg: signing failed: Inappropriate ioctl for device

try the following steps

Test if gpg is actually working:

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echo "test" | gpg2 --clearsign

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If you get error like this: 

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[root@localhost]# echo "test" | gpg2 --clearsign
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

test
gpg: signing failed: Inappropriate ioctl for device
gpg: [stdin]: clear-sign failed: Inappropriate ioctl for device 

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then try the following:

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[root@localhost]# export GPG_TTY=$(tty)

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If this fixes the problem, add it to your .bashrc or .bash_profile file