diff --git a/docker/alpine.Dockerfile b/docker/alpine.Dockerfile
index 36f9f40a5..f36660f32 100644
--- a/docker/alpine.Dockerfile
+++ b/docker/alpine.Dockerfile
@@ -3,7 +3,19 @@ FROM alpine:3.13
 ENV LANG C.UTF-8
 ENV LC_ALL C.UTF-8
 
-RUN apk add bash cmake g++ gettext-dev git libintl musl-dev ncurses-dev ninja python3 py3-pexpect
+RUN apk add --no-cache \
+  bash \
+  cmake \
+  g++ \
+  gettext-dev \
+  git \
+  libintl \
+  musl-dev \
+  ncurses-dev \
+  ninja \
+  pcre2-dev \
+  python3 \
+  py3-pexpect
 
 RUN addgroup -g 1000 fishuser
 
diff --git a/docker/bionic-asan-clang.Dockerfile b/docker/bionic-asan-clang.Dockerfile
index dfdbd086a..a53249fa4 100644
--- a/docker/bionic-asan-clang.Dockerfile
+++ b/docker/bionic-asan-clang.Dockerfile
@@ -2,11 +2,6 @@ FROM ubuntu:18.04
 
 ENV LANG C.UTF-8
 ENV LC_ALL C.UTF-8
-ENV CXXFLAGS="-fno-omit-frame-pointer -fsanitize=undefined -fsanitize=address" \
-  CC=clang-9 \
-  CXX=clang++-9 \
-  ASAN_OPTIONS=check_initialization_order=1:detect_stack_use_after_return=1:detect_leaks=1 \
-  UBSAN_OPTIONS=print_stacktrace=1:report_error_type=1
 
 RUN apt-get update \
   && apt-get -y install \
@@ -16,12 +11,14 @@ RUN apt-get update \
     gettext \
     git \
     libncurses5-dev \
+    libpcre2-dev \
     locales \
     ninja-build \
     python3 \
     python3-pexpect \
     sudo \
-  && locale-gen en_US.UTF-8
+  && locale-gen en_US.UTF-8 \
+  && apt-get clean
 
 RUN groupadd -g 1000 fishuser \
   && useradd -p $(openssl passwd -1 fish) -d /home/fishuser -m -u 1000 -g 1000 fishuser \
@@ -35,4 +32,10 @@ WORKDIR /home/fishuser
 
 COPY fish_run_tests.sh /
 
+ENV CXXFLAGS="-fno-omit-frame-pointer -fsanitize=undefined -fsanitize=address" \
+  CC=clang-9 \
+  CXX=clang++-9 \
+  ASAN_OPTIONS=check_initialization_order=1:detect_stack_use_after_return=1:detect_leaks=1 \
+  UBSAN_OPTIONS=print_stacktrace=1:report_error_type=1
+
 CMD /fish_run_tests.sh
diff --git a/docker/bionic-tsan-clang.Dockerfile b/docker/bionic-tsan-clang.Dockerfile
index 9efb0eb6d..4e105021c 100644
--- a/docker/bionic-tsan-clang.Dockerfile
+++ b/docker/bionic-tsan-clang.Dockerfile
@@ -2,7 +2,6 @@ FROM ubuntu:18.04
 
 ENV LANG C.UTF-8
 ENV LC_ALL C.UTF-8
-ENV CXXFLAGS="-fsanitize=thread" CC=clang-9 CXX=clang++-9
 
 RUN apt-get update \
   && apt-get -y install \
@@ -12,12 +11,14 @@ RUN apt-get update \
     gettext \
     git \
     libncurses5-dev \
+    libpcre2-dev \
     locales \
     ninja-build \
     python3 \
     python3-pexpect \
     sudo \
-  && locale-gen en_US.UTF-8
+  && locale-gen en_US.UTF-8 \
+  && apt-get clean
 
 RUN groupadd -g 1000 fishuser \
   && useradd -p $(openssl passwd -1 fish) -d /home/fishuser -m -u 1000 -g 1000 fishuser \
@@ -31,4 +32,5 @@ WORKDIR /home/fishuser
 
 COPY fish_run_tests.sh /
 
+ENV CXXFLAGS="-fsanitize=thread" CC=clang-9 CXX=clang++-9
 CMD /fish_run_tests.sh
diff --git a/docker/bionic-tsan.Dockerfile b/docker/bionic-tsan.Dockerfile
index 1ee2f2d86..3ef16a917 100644
--- a/docker/bionic-tsan.Dockerfile
+++ b/docker/bionic-tsan.Dockerfile
@@ -2,21 +2,23 @@ FROM ubuntu:18.04
 
 ENV LANG C.UTF-8
 ENV LC_ALL C.UTF-8
-ENV CXXFLAGS "-fsanitize=thread"
 
 RUN apt-get update \
   && apt-get -y install \
     build-essential \
     cmake \
+    clang-9 \
     gettext \
     git \
     libncurses5-dev \
+    libpcre2-dev \
     locales \
     ninja-build \
     python3 \
     python3-pexpect \
     sudo \
-  && locale-gen en_US.UTF-8
+  && locale-gen en_US.UTF-8 \
+  && apt-get clean
 
 RUN groupadd -g 1000 fishuser \
   && useradd -p $(openssl passwd -1 fish) -d /home/fishuser -m -u 1000 -g 1000 fishuser \
@@ -30,4 +32,5 @@ WORKDIR /home/fishuser
 
 COPY fish_run_tests.sh /
 
+ENV CXXFLAGS "-fsanitize=thread"
 CMD /fish_run_tests.sh
diff --git a/docker/bionic.Dockerfile b/docker/bionic.Dockerfile
index 4cab03585..05694550a 100644
--- a/docker/bionic.Dockerfile
+++ b/docker/bionic.Dockerfile
@@ -7,15 +7,18 @@ RUN apt-get update \
   && apt-get -y install \
     build-essential \
     cmake \
+    clang-9 \
     gettext \
     git \
     libncurses5-dev \
+    libpcre2-dev \
     locales \
     ninja-build \
     python3 \
     python3-pexpect \
     sudo \
-  && locale-gen en_US.UTF-8
+  && locale-gen en_US.UTF-8 \
+  && apt-get clean
 
 RUN groupadd -g 1000 fishuser \
   && useradd -p $(openssl passwd -1 fish) -d /home/fishuser -m -u 1000 -g 1000 fishuser \
@@ -29,4 +32,5 @@ WORKDIR /home/fishuser
 
 COPY fish_run_tests.sh /
 
+
 CMD /fish_run_tests.sh
diff --git a/docker/centos7.Dockerfile b/docker/centos7.Dockerfile
index 2286e6700..663ccd98a 100644
--- a/docker/centos7.Dockerfile
+++ b/docker/centos7.Dockerfile
@@ -10,7 +10,9 @@ RUN yum install --assumeyes epel-release https://repo.ius.io/ius-release-el7.rpm
     ninja-build \
     python3 \
     openssl \
-    sudo
+    pcre2-devel \
+    sudo \
+  && yum clean all
 
 # cmake is called "cmake3" on centos7.
 RUN ln -s /usr/bin/cmake3 /usr/bin/cmake \
diff --git a/docker/centos8.Dockerfile b/docker/centos8.Dockerfile
index 741dc2433..3ab81ff17 100644
--- a/docker/centos8.Dockerfile
+++ b/docker/centos8.Dockerfile
@@ -1,5 +1,12 @@
 FROM centos:8
 
+# See https://stackoverflow.com/questions/70963985/error-failed-to-download-metadata-for-repo-appstream-cannot-prepare-internal
+
+RUN cd /etc/yum.repos.d/ && \
+  sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-* && \
+  sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*
+
+
 # install powertools to get ninja-build
 RUN dnf -y install dnf-plugins-core \
   && dnf config-manager --set-enabled powertools \
@@ -13,7 +20,9 @@ RUN dnf -y install dnf-plugins-core \
     ninja-build \
     python3 \
     openssl \
-    sudo
+    pcre2-devel \
+    sudo \
+  && yum clean all
 
 RUN pip3 install pexpect
 
diff --git a/docker/fedora.Dockerfile b/docker/fedora.Dockerfile
index 65f6d9528..9d48ccb40 100644
--- a/docker/fedora.Dockerfile
+++ b/docker/fedora.Dockerfile
@@ -1,15 +1,19 @@
 FROM fedora:latest
 
 RUN dnf install --assumeyes \
-    cmake \
-    gcc-c++ \
-    git-core \
-    ncurses-devel \
-    ninja-build \
-    python3 \
-    python3-pip \
-    openssl \
-    sudo
+      cmake \
+      diffutils \
+      gcc-c++ \
+      git-core \
+      ncurses-devel \
+      ninja-build \
+      pcre2-devel \
+      python3 \
+      python3-pip \
+      openssl \
+      procps \
+      sudo && \
+    dnf clean all
 
 RUN pip3 install pexpect
 
diff --git a/docker/focal-32bit.Dockerfile b/docker/focal-32bit.Dockerfile
index bf5bd2b10..228fece30 100644
--- a/docker/focal-32bit.Dockerfile
+++ b/docker/focal-32bit.Dockerfile
@@ -19,7 +19,8 @@ RUN apt-get update \
     python3 \
     python3-pexpect \
     sudo \
-  && locale-gen en_US.UTF-8
+  && locale-gen en_US.UTF-8 \
+  && apt-get clean
 
 RUN groupadd -g 1000 fishuser \
   && useradd -p $(openssl passwd -1 fish) -d /home/fishuser -m -u 1000 -g 1000 fishuser \
diff --git a/docker/xenial.Dockerfile b/docker/xenial.Dockerfile
index 9e374f662..a0b7896d7 100644
--- a/docker/xenial.Dockerfile
+++ b/docker/xenial.Dockerfile
@@ -10,12 +10,14 @@ RUN apt-get update \
     gettext \
     git \
     libncurses5-dev \
+    libpcre2-dev \
     locales \
     ninja-build \
     python3 \
     python3-pip \
     sudo \
-  && locale-gen en_US.UTF-8
+  && locale-gen en_US.UTF-8 \
+  && apt-get clean
 
 # The python3-pexpect package on Xenial doesn't allow delaybeforesend to be None.
 # Install pexpect with pip which is newer.