How To Fix “unable to lock database” Error In Arch Linux

The other day, I was about to update my Arch Linux system. When I issued the following command to update Arch Linux server, it showed an error, and won't let me to install any package or remove any package.

# pacman -Syu

Sample output:

:: Synchronizing package databases...
error: failed to update core (unable to lock database)
error: failed to update extra (unable to lock database)
error: failed to update community (unable to lock database)
error: failed to update multilib (unable to lock database)
error: failed to synchronize any databases
error: failed to init transaction (unable to lock database)
error: could not lock database: File exists
 if you're sure a package manager is not already
 running, you can remove /var/lib/pacman/db.lck

The beauty of Linux distros is sometimes they will the explicitly display the solution along with the error message. As you can see in the above output, it says: "..you can remove /var/lib/pacman/db.lck".

So, I simply deleted the aforementioned file with command:

$ sudo rm /var/lib/pacman/db.lck

Voila! It worked. I can then able to update, install and remove without any problems.

$ pacman -Syu

Sample output:

:: Synchronizing package databases...
 core 122.8 KiB 162K/s 00:01 [######################] 100%
 extra 1771.8 KiB 249K/s 00:07 [######################] 100%
 community 3.3 MiB 256K/s 00:13 [######################] 100%
 multilib 163.5 KiB 265K/s 00:01 [######################] 100%
:: Starting full system upgrade...
resolving dependencies...
looking for conflicting packages...

Packages (8) ca-certificates-mozilla-3.22-1 coreutils-8.25-1 curl-7.47.1-1
 gcc-5.3.0-4 gcc-libs-5.3.0-4 libgcrypt-1.6.5-1 nano-2.5.2-1
 pacman-mirrorlist-20160208-2

Total Download Size: 42.79 MiB
Total Installed Size: 187.90 MiB
Net Upgrade Size: 0.91 MiB

:: Proceed with installation? [Y/n] y
:: Retrieving packages ...
 gcc-libs-5.3.0-4-x86_64 12.7 MiB 261K/s 00:50 [######################] 100%
 coreutils-8.25-1-x86_64 2.1 MiB 262K/s 00:08 [######################] 100%
 ca-certificates-moz... 363.0 KiB 241K/s 00:02 [######################] 100%
 curl-7.47.1-1-x86_64 798.3 KiB 263K/s 00:03 [######################] 100%
 gcc-5.3.0-4-x86_64 26.1 MiB 247K/s 01:48 [######################] 100%
 libgcrypt-1.6.5-1-x... 403.5 KiB 244K/s 00:02 [######################] 100%
 nano-2.5.2-1-x86_64 407.0 KiB 262K/s 00:02 [######################] 100%
 pacman-mirrorlist-2... 5.3 KiB 408K/s 00:00 [######################] 100%
(8/8) checking keys in keyring [######################] 100%
(8/8) checking package integrity [######################] 100%
(8/8) loading package files [######################] 100%
(8/8) checking for file conflicts [######################] 100%
(8/8) checking available disk space [######################] 100%
:: Processing package changes...
(1/8) upgrading gcc-libs [######################] 100%
(2/8) upgrading coreutils [######################] 100%
(3/8) upgrading ca-certificates-mozilla [######################] 100%
(4/8) upgrading curl [######################] 100%
(5/8) upgrading gcc [######################] 100%
(6/8) upgrading libgcrypt [######################] 100%
(7/8) upgrading nano [######################] 100%
(8/8) upgrading pacman-mirrorlist [######################] 100%
warning: /etc/pacman.d/mirrorlist installed as /etc/pacman.d/mirrorlist.pacnew

Hope this helps.